Automotive Electrical Schematic Diagnosis - Intermediate Course | Steven Liguori | Skillshare

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Automotive Electrical Schematic Diagnosis - Intermediate Course

teacher avatar Steven Liguori, Teaching is My Passion

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Taught by industry leaders & working professionals
Topics include illustration, design, photography, and more

Watch this class and thousands more

Get unlimited access to every class
Taught by industry leaders & working professionals
Topics include illustration, design, photography, and more

Lessons in This Class

29 Lessons (3h 5m)
    • 1. Video 1 Introduction

    • 2. Video 0 Welcome Course Preview

    • 3. Video 2 Introductory Course Review

    • 4. Video 3 Review What Every Circuit Needs

    • 5. Video 4 Review Series and Parallel Circuit Differences

    • 6. Video 5 Review Horn Schematic Explained

    • 7. Video 6 Automotive Electrical Terms Assessment 1

    • 8. Video 7 Diagnostic Practical Assessment

    • 9. Video 8 Diagnostic Practical Assessment Review

    • 10. Video 9 Power Side and Ground Side Switches

    • 11. Video 10 Power Side and Ground Side Switches Highlighting

    • 12. Video 11 Real World Diagnostic Considerations

    • 13. Video 12 Information Circuits

    • 14. Video 13 Modules Inputs and Outputs

    • 15. Video 14 Trunk Release Schematic Explained

    • 16. Video 15 Trunk Release Schematic Highlighted

    • 17. Video 16 Trunk Release Schematic Fault 1

    • 18. Video 17 Trunk Release Schematic Fault 2

    • 19. Video 18 Trunk Release Schematic Fault 3

    • 20. Video 19 Coolant Fan Schematic Explained

    • 21. Video 20 Coolant Fan Schematic Highlighted OFF

    • 22. Video 21 Coolant Fan Schematic Highlighted Low Speed

    • 23. Video 22 Coolant Fan Schematic Highlighted High Speed

    • 24. Video 23 Coolant Fan Fault Low Speed INOP

    • 25. Video 24 Coolant Fan Fault High Speed INOP

    • 26. Video 25 A Little Bit About Scanners

    • 27. Video 26 Cooling Fan Fault All Fans Inop

    • 28. Video 27 Cooling Fan Faults Reverse Psychology Diagnostics

    • 29. Video 28 Before You Blame the Module and Next Steps

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About This Class

This Intermediate Automotive Electrical Schematic Diagnostic Course takes over where the Beginner Course left off, Reinforcing and Enhancing your Understanding of Automotive Electrical Schematic Diagnosis.

Although not required, it is Recommended that you Complete the Beginner Course before moving on to this Intermediate Course. The practice activities from the first course lay the groundwork necessary to allow for a smooth transition to the more complex diagrams in this course.

While Course One explains the Foundation Material necessary to Understand many Basic Electrical circuits, This Course will explore Module and Information Circuits in Detail on several schematics, so you can Apply the Knowledge to ANY Schematic. 

From his Experience Teaching Thousands of Students over the years, Automotive Service Excellence (ASE) Master Technician and Instructor Steve Liguori has found that students become more adept if they have a solid understanding of a few schematics and the ability to apply that understanding to any schematic.

By Understanding the Basics of Module and Information Circuits, you will find that Your Ability to Diagnose other Systems on the car including, Starting, Charging, Power Windows, Door Locks, Heating and Air Conditioning and Body Electrical will Improve Significantly.

Let's Get Started!

Meet Your Teacher

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Steven Liguori

Teaching is My Passion


A Tale of Two Careers….


Steve has been trading Stocks and Options since 1999.  With his passion for teaching, he has been a perfect fit as an Options Coach/Mentor for three Online Trading Education Companies.  The Founder and Options Coach at, Steve is available to answer your questions as well as provide One-on-One Online Personal Coaching Sessions.

Years of Coaching new and experienced Traders has given Steve the understanding of what struggling traders need most, clear explanations of the Processes that will lead them to the Success they are looking for in their Trading.


Prior to becoming a Full Time Trader, Steve was and still is an ASE Certified Master Automotive Technician.  He was... See full profile

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1. Video 1 Introduction: welcome to the do it yourself automotive electrical diagnostic intermediate course. In this programme, we will explore more advanced automotive electrical schematics. Yes, the word advanced can sound a little scary, but there's no need to worry. The basic electrical fundamentals learned in the first course will be enhanced and applied to module and information circuits. Complex schematics fall into two categories. The schematic either has multiple components or systems on the same page, and we have to recognize and focus on the components and wiring that pertain to the circuit We're diagnosing. An example of this would be the engine controls schematic. You may just need Teoh diagnosis, the coolant temperature sensor. But when you go to the schematic, it's going to show you quite a few sensors that pertain to the engine controls. So you have to find on that picture the information that you need. The second category is that the system or component we're diagnosing has 234 or even mawr power load and ground circuits that all work together to produce an end result. An example of that could be the trunk release schematic where you might have a switch monitoring circuit. You might have a module that controls a relay that would be a circuit for that, and then you would have another circuit that's just for the actuator. So all three of these circuits must be in good working water to allow the trunk release to function properly. Our job would be to diagnose all of those and decide which one of those circuits is not working, and then find the fault in that one circuit. With practice and a little determination, you will find that your understanding and confidence will improve enormously. 2. Video 0 Welcome Course Preview: welcome to the do it yourself automotive electrical diagnostic Intermediate course. My name is Steve Allegory. I'm a master automotive technician. For over 35 years, I have worked in dealerships for over 25 years, mostly as an electrical specialist. It was my job to figure out the problems that most people couldn't fix. In my 10 plus years of teaching, I've also educated thousands of students in automotive, electrical and electron ICS. In this course, I want to add to the foundation material from the first course and introduce some more complex schematics. Since there are so many makes and models out there today, it is impossible to explain how every system of every vehicle works. In my experience teaching over the years, I've found that the best way to develop your understanding of electrical is to demonstrate the principles in detail on a few schematics and explain how to apply these principles to any schematic. This course will focus on information circuits like switches and sensors, as well as module circuits like the body computer and the engine computer. Once you learn and practice the diagnostic process I teach in this course, you will be amazed at how spending a little time looking at the schematic can save you time , money and aggravation. Sometimes you just need to go out to the car, verify the concern, find the proper schematic for the car and spend a little time with it. Remember that when diagnosing electrical, you're going toe work like a detective eliminating all of the potential suspects or possibilities until there is only one left. And then that component or part of the circuit has to be guilty. Now, if you're going to repair your own car, it's going to require that you take some type of a hands on course to make sure you have the skills and safety precautions necessary. Be careful about jumping right in and testing something on your car until you're comfortable and feel you've acquired the skills to do so. So with that said, let's get started 3. Video 2 Introductory Course Review: the next few lessons are comprised of a bridge segments from the first course to refresh your memory and help prepare you for the new concepts you will learn in this course. If you feel confident that you understand the information in the following three review videos, feel free to skip ahead to video six. Where you can test your knowledge with a short practice quiz. If you need a clearer explanation of any of the topics, refer to Lessons three through 10 in the introductory course. 4. Video 3 Review What Every Circuit Needs: every electrical circuit on the car really just needs three things. In order for the circuit to operate, we need to have a power supply, which would be the battery or the alternator. When the car is running, we need the power side of the circuit, which includes the supply wiring all the way up to the load. The load of the circuit is the part of the circuit that's designed to operate or use the voltage. So an example of that would be the horn or the headlights or the tail lights or the blower motor, the starter motor, all of those air loads. The third thing that we need in order for a circuit toe work is the ground path, and the ground path includes the wiring from the load back to the battery, and this can also include the metal frame of the vehicle, often times and in many or most cases, the metal frame of the vehicle is used for the ground path because it eliminates the need for extra wiring all the way back to the battery for each particular circuit on the car. If you use the metal frame of the car, it eliminates some of the wiring that you might have to run, which anything that they can do to eliminate wait can increase gas mileage and performance , so that's why they do it. 5. Video 4 Review Series and Parallel Circuit Differences: in this video, we're gonna go over the differences between Siri's and parallel circuits on the left. Here I have to Siri's circuits. The top circuit is showing an open circuit. Noticed that the switch is open on the bottom picture. I have to switch closed and notice that the bulbs are lit now. Noticed that on the left the bulbs are lit a little bit dimmer than they are in the pictures. On the right. On the right, I have a parallel circuit, and again I have a switch. And this one switch, if it was turned on, would control both of these bulbs. So in the bottom picture, I'm showing this which closed? Notice how both of the bulbs are lit and notice also that they're lit brighter than the bulbs are in the series circuit. So this brings us to our first difference between series and parallel circuits. The first differences if you use a serie circuit and use multiple loads or multiple bulbs. So what happens here is when we want to have to devices use less than 12 volts. We put them in a series circuit so that they share the voltage. So one example of this would be on daytime running lights. Some manufacturers will wire the bulbs in Siris so that they share the voltage, and then because they're sharing the 12 volts, let's say they're sharing it equally. That would mean that this topple would get six bolts and the bottom bold would get six polls. So because of that, the amount of the voltage that the bulb is actually getting is gonna factor into how bright that bulb will be. And in the parallel circuit, the reason that a parallel circuit is used more often and automotive is that we want each individual circuit that were operating most of the time, like the blower motor or the radio or the window motor or the door locks. They're all 12 volt circuits, and we want them to each have their own 12 volt circuit, so they wire. Most of the most of the schematics, and drawings on the car are in parallel because we want each device to be able to have that 12 volts available. But for the cases where we do want them to have less voltage, one of the ways that they'll do it is by putting things in Siris. There's also a device called a resistor that you could put into the picture to where, if I put a resistor in this picture right here on this parallel path of this one bulb, the resistor would use up some of the voltage, and the bold would use up some of the voltage. So if I didn't want to put the two bulbs in Siris, I could then add in a resistor in part of the circuit where I wanted it to be dimmer. Or I wanted this voltage to be less up here, and that would also do the same thing. The main difference here that we're referring to for Siris in parallel circuits is Syriza's used when we want them to share and series circuits means Onley. One path and a parallel circuit is used when we want each device toe, have 12 volts available to it and noticed that a parallel circuit is just made up of a couple of Siri circuits where a part of the circuit is shared. If I was to draw a line from here and went all around the path through this first bulb, notice how I could come back to the battery. And if I just looked at the part that I just highlighted, that's a serious circuit. And let's say I was gonna make a separate Siri's circuit where I'm doing the same thing, but this time only for bold, too. So if I then highlight this picture coming around here and down and all the way back, and I just ignored this for now, wouldn't that also be a second series circuit? So a parallel circuit is just where we're putting to Siri circuits orm or together where a part of the circuit is similar. So in this picture they're using the same battery. They're using the same fuse. They're using the same switch. But there's a point where the circuit splits. And then there's a point where it comes back together. And the good news for this is in a parallel circuit. If this is a 12 volt circuit, each of these branches of the circuit or legs of the circuit, as they're sometimes called, has 12 volts available to it, which is why these bulbs are bright and the other good part about a parallel circuit, which is most important is if there was a fault in here, for example, an open circuit that makes this bulb go out, then this side, this path or this leg of the circuit would not be affected as long as the open is inside this branch or inside this path. Now, if I had an open in the circuit that was over here, that would affect this bulb. But it wouldn't affect that bull because the full path for this bulb is still intact Now. In 1/3 scenario, if I had an open down here in the ground path that was on the way back to the battery, this ground path is needed by each of the pats, the path for bold one and the path for bulb to. So if there was an open in this part of the circuit, that would actually affect both bulbs in the same way that if the fuse was blown, it would affect both bulbs because that would be just a Ziff. There's an open in the part of the circuit that they both need. So the disadvantage to Siri's is that if there's a fault anywhere in the circuit, then the whole circuit becomes dead. But in a parallel circuit as long as the fault is in a particular section of the circuit than it won't affect all of the other devices. The parallel circuit is used extensively in automotive because it allows the two main concepts it allows each branch of the circuit to have the full voltage. And the second main big difference and big deal that we need is that if there's a fault in one of the branches, it won't affect the other. 6. Video 5 Review Horn Schematic Explained: This is a horn schematic from a General Motors vehicle, which uses a relate to control the horns. And a relay is a device that allows a low current path in the circuit. So this would be the low current path here, the really coil, and in this case we have two different ways of turning it on. We can use either the horn switch or the body control module, or BCM can turn on the horn relay as well from a signal from the theft deterrent module. And that kind of information about the circuit and the way it operates there is usually in the manufacturer's manuals. There is a section called Description and Operation, which on occasion it could be part of the schematic, where they describe how it operates. But most of the time it's in a separate section where you find this description and Operation page, and it will describe how that particular circuit work so it might say something in words. Power is supplied through a 10 AM views to the relay coil of the horn relay, and a ground path is supplied by either pressing the horn switch or through the BCM relate control when it gets a signal from the theft deterrent module. And then when the Reedley is activated, it closes thes switch inside the horn relay and allows the 20 AMP circuit to power up the horn. And in this case, we have a dual horn assembly, so description operation is there for when you need further clarification, where you can understand the picture just from the way it's laid out. Now on this picture, you pretty much can understand most of what's going on. Maybe you wouldn't know when the BCM would be using this horn control circuit, but with the description and operation they're telling you, it turns on when the theft deterrent module sends a signal to the BCM, or when you're hitting the panic button on your remote control for the car to outline the two pats for power load and ground. Let's just take a quick look and highlight thes two pads. The power side of the circuit would be everything up from where the 12 volts is supplied all the way to the relay coil, and the relay coil itself is the load here. This is the part that's going to use up the voltage and remember relays gun electromagnet Like when you were in school science class. When you were younger and you took a piece of wire and wrapped it around a metal nail, it would become an electro magnet. And inside a relay, they've just taken very thin wire and wrapped it thousands of times around a piece of metal core that becomes the electromagnet. Just like the experiment you didn't school. That's what will pull this switch over when we give power and ground to the wire that is connected to the nail, which in this case, is the relay coil instead of a nail. The ground path would be then everything from the bottom of the really coil all the way to the ground. And like I said before in this case, either switch could be the ground for this. So I could either press the horn switch and I would have my ground path through here. Or if I hit the panic button on my remote, the BCM would get the signal from the theft of terror module, and it would close this, which and that would give me the completion of the ground path in this direction over here . Now let's look at the power load and ground on the switch side of the relay. We would have the power side would be everything from where it's 12 volts up until and now this which would be closed when the relays activated. And the power side would be all the way through the relay switch and up to the positive side of the horn assembly itself, where inside the 12 volts would actually be available all the way up to where the horn coil starts on each horn. And then the load would be the horns themselves. And then the ground path would be this area underneath. And in this case, the horns. Aaron Parallel. So they both get 12 volts so that they can sound nice and loud. And this ground path is shared by both horns down to here. 7. Video 6 Automotive Electrical Terms Assessment 1: before we move forward. Let's see if you remember some automotive electrical terms from the first course, you can pause the video and write down your answers or print the quiz and answer key by clicking on the downloadable materials for this lesson. When you are ready, move on to the diagnostic practice assessment in the next lesson. 8. Video 7 Diagnostic Practical Assessment: I hope you did well on the electrical terms assessment in the last video. Refer back to Lessons three through 10 in the beginner's course. If you would like to review these topics in this video, I want to give you a chance to test your skills. You can download the schematic, the questions and the answers from the additional resource is for this lesson for some of you that would rather skip the download. I will leave the questions on the screen for 30 seconds and then the schematic for 30 seconds. This way you can move back and forth in the video. As you answer each question In the next video, we will go over the answers. Good luck. 9. Video 8 Diagnostic Practical Assessment Review: Okay, so let's see how you did on the diagnostic practice assessment. Question one based on the schematic. How much voltage do you expect to measure at point C if this circuit is working properly? So it's asking you what is meter one saying If you would hook up meter one with the red lead at point C in the black Leavitt ground, we're measuring the voltage at point C and what you'd expect to measure is 12 volts because the power supply here is 12 volts. And if everything is working properly, you should get that 12 volts at point C. If this wire is good, So the correct answer for question one is choice a 12 volts. Number two, If you measure 12 volts at terminal C of the 10 AMP. Fuse and zero volts at point D of the 10 AM fuse, this means that blank is bad. This is saying that you're measuring 12 volts at point C, but you're only measuring zero volts at point D. That means that you lost the voltage somewhere in between point C and D, which in this case would mean that the fuse was blown when you're measuring fuses with a volt meter. There's really just three sets of readings that you can get your either going to get 12 volts here and 12 volts here, which means the fuses good. You could get 12 olds here and zero volts here, which means the fuses blown. Or you could get zero volts here and zero volts here, which really doesn't tell you anything about the fuse. It tells you that the voltage is not getting to the fuse, so it means that there is a problem going back in this direction, and you would have to look back in the power distribution schematics to find the location of what supplies the 12 volts to this point. So the correct answer for Question two was choice. See, the tenant fuses bed because we were getting 12 goals at sea and zero volts at the question . Three. If you measure 12 volts at terminal F of the horns, which that's right down here, meter number four. When you press the warrant switch to activate the horn, it doesn't work, and you still measure 12 volts at Terminal F. What does this mean? So it's saying that you're measuring 12 volts here at Terminal F, regardless of if you're closing the switch or not. Now, by design, it's normal to measure 12 volts here before you press the switch. Because this 12 volts will be on this wire all the way to this point until the switch closes and provides a ground path. Once the ground path is provided, this load will now activate and use up the 12 volts, and then there will be 12 volts. From here to here, the load will use the voltage, and then the rest of this path will be at zero volts. So in this case, because the voltage is not changing from 12 to 0 when we close the switch, it means that either the switch is open, even though we're physically closing it. It could be broken inside where it's not allowing the path to go from F to G. And it also could mean that the ground path between point G and ground his bed. So getting the 12 volts here after you press the switch, it doesn't automatically mean the switches bad. It just means there's no ground path, and in this case it means it's either the switch or the ground path. So the correct answer for a question three is Choice D. Both A and B were correct where a was talking about the horns, which may be faulty, and B was talking about the wire between terminal G and ground may be faulty. So since both of those are possible, the correct answer is D Both A and B. You're correct question for And this question is also referring to the horn switch being pressed. They're saying that you're measuring 12 volts at meter number three, which is measuring the power side of the relay switch. But you're only measuring eight volts at meter number six. And if the switch was activated, we would expect that 12 volts that was here to easily get to this point if the relate was good and because we're only getting eight volts at this point on meter six, it means that inside the relay, the switch is using up some of the voltage. And this is caused by there being high resistance on the switch itself or the contact between the switch lever and this terminal right here. So when you have a high resistance problem, it robs some of the voltage from getting to the device that you want to get to. So what would that cause? It would cause the horn to sound sick or lower in tone. Or if the high resistance becomes large enough and it only allows a few volts to get to the horn, it may actually not even work at all. So in this case, the correct answer is the switch. The relay switch is bad, and it has high resistance. So the correct answer for this question would be choice. See the one release, which has high resistance? Let's move on to number five. The last question. The horn does not work at all. If you measure 12 volts on meter five, when the horn switches pressed, this means what? So we're talking about meter five over here, and if you measure 12 volts on the ground side of the horn when the switch is pressed, that's like Question three. It's telling you that there's no ground path. We expect to measure 12 volts on the power side of the war in, and we expect to measure zero volts on the ground side of the horn. So if I'm measuring 12 volts on this side on the ground side. When the horn is activated, it means that there is no path between this point and ground. It's just saying that there's an open ground, and that's what you where you would need to look to fix it. Maybe it could be a G 101 Maybe it could be the wiring in between now if it was G 101 because there were other wires that funnel into this same ground. Then if it was G 101 it would cause multiple things to not be working. So if it's on Lee the horn that's not working, your fault would be between the ground side of the horn and this junction point here. And that's where you would find the open if we were doing this live on a car. So the correct answer for Question five is Choice D. The ground for the horn assembly is open, so I hope you did well on this. And if you did, I think you're more than ready to move on to the next section, which will introduce a couple variations of switches and then show you informational switches where we start to get into computers and modules and how they use switches to provide information, so I'll see you in the next video. 10. Video 9 Power Side and Ground Side Switches: in this video, we're gonna look at two different ways of putting the switch in the circuit. The one is the power side switch and the others the ground side switch. And if you notice on this picture, the same components are present in both circuits. They both have a fuse. They both have a switch, and they both have a bowl. The difference is in the power side switch. The load and the ground path are always there, and the switch is completing the power path on the ground side switch the power part of the circuit and the load are always there, and it's the ground sides path that is being completed by the switch. Let's take a look at what the voltages would be at the different points in the circuit and see how they differ. If we were diagnosing this type of circuit, so notice on the power side switch that you would have 12 volts all the way up until the actual tip of the switches where you would have it and the whole rest of the circuit the bulb included. If you were measuring it when the circuit was off, you would have zero volts and on the ground sites, which you would actually have 12 volts all the way down to the bulb and on the ground side of the bulb and all the way up to the tip of the switch, even when the circuit is off. So think how confusing that could be for somebody that doesn't understand this. Their headlights air off and they go out to the car, and they measure 12 volts on both sides of the headlight. While it's off now to you, you realize that that just means that there's a switch in the ground path that's not activated right now. But to them, they could be thinking many things shorted headlight wiring. When people don't know, they usually use the word short. And while a short can happen in some cases, it's Most of the faults on cars are opens where something's disconnected when something shorted. It just means it has less resistance than it's supposed to. And while that does happen on occasion, it's just not what most of the faults are. Most of the faults are opens, so what we're gonna do in the next video is we're gonna look at the power side and the ground side switch in both the off position. And then I've redrawn the circuits in the next video so that they're both on as well. And I want to show you a way of highlighting the circuit using three colors where if you did this and practiced it with several different circuits, it would help you get a really good understanding of the power load and ground side of the circuit and where you would expect to measure the 12 volts and the zero volts. So as we move into the next video, if you have a way of printing the schematics, which will be in the traditional materials, additional resource is I would recommend that you print them out and get yourself three color highlighters, the three colors that I'm going to use our orange, green and yellow. But that's just my personal preference. You just need to identify which ones are gonna be the 12 volt color. Which one's going to be the zero volt color and which one's going to be the color that you use for the load when it's using up the voltage, So I'll see you in the next video and Hopefully you'll be able to highlight along with me and we will get a deeper understanding of how these circuits operate. 11. Video 10 Power Side and Ground Side Switches Highlighting: So here I have the power side and ground side switch circuits again. But this time I have drawn them to different times once with the circuit off and once with the circuit on for the power side switch and the same thing for the ground sites, which I have the circuit drawn in the off position. And then I redrew the circuit, closed the switch so that we can simulate what the readings would be if the circuit was on . And what I want to do here is I want to do to activities I first wanna have you fill in what all of the voltages would be at these different points in the circuit. So everywhere that there's a dot and then again at the bottom at the ground, I'd like you to pause the video and print out the schematic from the resource is if you can , And right in what you think the voltages would be at that point for the off position theon position, and then again for the ground side switch for the off position and then for the on position . And if you do this, you will wind up getting the most out of this activity. The second thing I want to do is after we get those voltages labeled on the page, I want to highlight the schematics in three different colors where we're using one color for labelling everywhere on the picture that we expect 12 volts a different color for everywhere on the picture, we expect zero volts and 1/3 color for everywhere. We're highlighting a load that is using up the voltage, so the three colors I'm using. Like I stated in the last video, I will be using orange for the power side or where I expect 12 volts, zero volts. I will use the color yellow, and I'll use the color green for any of the loads that are using the voltage. So I would not color this load green because it's not using up any voltage. But I would highlight this load green because it is using voltage. So pause the video for a few seconds and label in all of the voltages on the page. Then start up the video, and I will put down all of the vultures for you so you can check your work and then after that, will pause the video again and highlight the schematic with whatever three colors you're using and then start up the video again and compared to what I have on the screen. And once again, you would not believe how good you will get it. This. If you spend the time to label the voltages on your schematic and then highlight the schematic, you'll wind up where you'll pick up a new schematic for the first time, and you'll start to recognize what the voltages that you expect to be at those locations. You'll you'll see it almost as if it's standing out on the page talking to you, because you you've gotten the understanding of what they should be, and then it's visible to you because now you know what you're doing. So pause the video and start labeling your voltages, Okay, so now I'm going to put the voltages that belong there on the screen and now, compared to what you had on your results. And as you see here, the 12 volts on the power sites, which would be all the way up to the tip of the switch and zero volts, would be from the ground path all the way up to the other side of the switch. So when you tried to figure out on a schematic how you would label it if you took your orange color in this case and highlighted all the way down from the power side all the way to the tip of the switch that would color in this picture the way it belongs. And then from the ground side, you would start all the way at the ground path where you expect zero and go all the way back up until you reach where the Open is. Because that open in the circuit is what's defining which side has 12 right now and which side has zero. Once you close the switch, it's gonna be a little bit different when you're highlighting, it's gonna be where the load is gonna be green because that's the part of the circuit that's using up the voltage. And then everything between the load and the 12 volts is gonna be orange, and then everything between the load and the ground is gonna be yellow. So take a second and pause the video again and see if you can label the ground sites, which is with the three colors like I've just done on the power side. Okay, so now let's compare what you've done to what I have on the screen. So as time goes by and with a little practice and repeating this activity on different schematics, you will be amazed at how the voltages will just pop out at you. Even if you're looking at a new schematic for the first time in the next video, we're going to talk about some diagnostic considerations. If you were actually working on a car, what the different voltages might be and how close you actually have to get to that exact voltage of 12 volts when you're thinking about the voltages you expect versus the voltages you might measure. So even though this isn't a hands on course, I want to give you some details about what voltages you might measure in the real world because they'd be different based on if the car was off or if the car was running. Because when the cars running, you're running off the alternator and you really have a different voltage to deal with. So when the next video, we'll talk a little more about that and what you can expect if you were actually working on your own car, 12. Video 11 Real World Diagnostic Considerations: We've been using 12 goals as the battery or supply voltage on the power side of the circuit since we've started talking about schematics. The truth is, though, in the real world, the car battery for most cars is 12.6 bolts. So what would that do to our diagnosis and our expectations of analyzing the circuit? And to further complicate things when the car is running, the alternator is charging the battery, and the voltage you might expect in the system at that time could be anywhere between 13.5 volts and maybe even as high as 14.5 holds or somewhere in between. So how does that affect the way we think about the different voltages that we should expect if we were actually going to make measurements on a car and utilize this information? And the answer is quite simple. We actually just want as close to whatever the source voltage is when we're measuring what's at the load. So, for example, if I have 12 volts as my battery, I would expect to get 12 volts right down here on the power side of the bulb when it's on. And if I wasn't getting 12 volts there, then I would want to know what part or what component, the wire or the switch or these other wires or the fuse. What other component has high resistance and is using up more voltage than it's supposed to , not allowing the correct voltage to get down to the bulb. Now, if the battery was 12.6, all that does is change what I expected. The Bold. I would then expect 12.6 at the ball if the car is running and the current battery voltage while it's running is 13.5 that I would expect to get 13.5 down at the bowl. If it was 14.5, I would expect 14.5 down at the bowl, and I would still expect zero on the other side of the circuit, regardless of what the voltages. Now it is normal to use up small amounts of voltage on pieces of wire or on the switch or in the ground path. So it is normal to lose that small amount of voltage up to, let's say, 1/2 of all. So if the battery voltage was 12 volts and I measured 11.6 or 11.8 down here a the bulb that would be considered okay. And on the other side of the circuit, I would expect to measure zero, and if it measured a couple 10th of a volt, it wouldn't be a big deal. You don't want to be off by more than 1/2 a volt. Compared to what? The battery voltages? To illustrate what the different voltage drops might be on different parts of the circuit. I've added seven meters to this power side switch that we have in the on position, and it's just showing you what you might expect if you had a live circuit and you actually measured all of the different voltage drops on the different parts of the circuit. So this first meter is just measuring the wire, the voltage that gets used up by the wire. That's between the 12 volt supply here and the fused. This second meter is measuring how much voltage is used up by the fuse. This third meter that how much is used up by the wire? How much is used up by the switch? This other wire? This is the important one. How much is being used up by the bulb. We would want that one to be 11.5 or more, and since it's 11.7 in this illustration, that would be acceptable. We just don't want to lose more than a total of about 1/2 a volt in the circuit. And we don't really want to lose more than about 2/10 of a vault, which would be 0.20 in any one section of the circuit, so you would rarely have to make all of these measurements. The only time that this comes into play is if you were expecting 12 volts to be used up by this bulb, and maybe it's only using nine. And if you had 12 volts at this location and you only had nine at this location, then you would need to make some tests on the way back to figure out where you were losing that other voltage. And these meters air actually hooked up across the different components. So this is called making a voltage drop measurement and voltage drop measurements can only be made when the circuit is active. In the other videos. When we were hooking up a meter and saying how much voltage is available. At a certain point, that's done a slightly different way. In those cases, the meter was connected to ground, and we were just monitoring how much voltage was available at any one point by hooking the red lead up to that point. I've put this in here just so you can get a little understanding that any part of the circuit that has resistance, even if it's a small amount of resistance or a tiny amount of resistance, it is gonna allow that part of the circuit to use thes very small amounts of voltage. And that will effect what the full voltage is that gets to the device that you're trying to power up. And the only time it comes into play where it's a problem is if too much of that voltage gets used up, not allowing that device, the bulb or the motor, or whatever it is to have the full voltage or the amount of voltage necessary to make it work properly. In the next video, we're gonna learn about the information circuits which use power, load and ground in a different way. So I'll see you in the next video 13. Video 12 Information Circuits: in this video, we're going to talk about information circuits. I'm gonna show you that once You understand the basic electrical circuits, like the power side switch over here and the ground sites which over here, the module information circuits are really not any more difficult. Sometimes what makes it seem harder is that there are so many information circuits on cars today. Some cars can have 50 to 100 or even mawr information circuits just to have the module. No thestreet Atis of a certain switch. The position of the accelerator, the position of the throttle, the temperature of the coolant, the temperature of the air, a thean today, the temperature in the ducks for your A C system. There are information circuits for most of the switches on the car, and all of these in most cases will each have their own circuit. The good news is it's still power, load and ground. So let's take a look over here. A to the power side switch and the information circuit. That's the power side switch. If I was to look at the numbers, the voltage numbers notice how I have a switch on the power side here a switch on the power side here. And when I close the switch, notice how the voltage changes and now I've either power up the bulb or in this case, I provide 12 volts down to where this meter is here. So inside the module, there's actually a meter on every one of these circuits monitoring the voltage in the regular circuit here. When I open and close to switch the light lights up or turns off. But in the information circuit, notice how the voltage just changes from 12 to 0 on this wire that's being monitored. The BCM knows the position of the switch. It knows if the switches on or off, if the switches on the voltage would be 12. And if the switches off the voltage would be zero and the only difference on the ground side switch. Now let's come over here to this side on the ground side switch. I have 12 volts past the load, just like I do over here. I have 12 volts past the load, and then when the switch closes, this reading up here is going to change that reading right after the load is going to change. So Let's watch that. So notice how that changes from 12 to 0 right after the low. This time inside the module, we have the load here, which is just a resistor. And this resistor could be a high resistance, which would allow very low current and very small wires to be used by the module So we don't need toe waste any power. We just need a way to monitor that. The voltage changed, so this resistor value could be 1000 owns. It could be 2000 homes, 10,000 homes. They can choose whatever value they feel they want to within certain limitations. But they're only trying to make a circuit using this resistor as the load so that they can monitor the change in voltage inside that circuit, once the switches closed or open here, notice that there's a different reading on the ground side switch. So on the power side switch we had 12 volts means closed and zero volts means open. But on the ground sides, which we have 12 volts means open and zero volts means closed. So the module's air just programmed to know that information on which type of switch it is and if there were multiple switches for a specific circuit, it would know all of that information programmed in by the manufacturer for all of the different switch circuits Now for us, when we're diagnosing them, we just need to know if there's a fault in that circuit or if there's a fault. Where why is the module not turning on a circuit? Maybe it doesn't think that this which is being pressed where maybe there is actually a fault in the switch itself, diagnosis becomes more of a three part process because you have an input circuit, the circuit that provides the information you have the module or the decision maker circuit . And then you have the output circuit or the device that is being activated, or the the load that you actually want to work, like a relay or or an injector. Whatever it ISS in the next video, we'll look into how modules use inputs and outputs in a little more detail 14. Video 13 Modules Inputs and Outputs: most modules on a car will have at least one input from a switch or a sensor in this illustration. On the left, we have switches or sensors as providing information, and I have them labeled inputs of top. Now there could be just one input for a specific action that's going to be needed where there could be multiple inputs, for example, if this was a body module or a door module that was monitoring if the doors were ajar. So there's a switch built into the latch. And when the door closes this, which will either open or closed depending on how it's designed so that the module knows if the door itself is opened or closed. Could they use a separate one of those switches for each door? So there could be four separate circuits if it's a four door car. But the module would make a decision to turn on the output, which in this case would be the door ajar light on your dash, regardless of if any one of them or all of them were not closed. Sometimes module circuits will look at the inputs and Onley. One input would be necessary for it to take a certain action, and the action in this case is whatever the output is. For this example, it was the door ajar light if we were talking about a different circuit like the air conditioning circuit. And let's say that the module is the engine computer and it wants to turn on the air conditioner or the clutch of the compressor, which would be the output device here. But we don't want to turn on the clutch of the compressor unless a few conditions are met. So that's what these inputs would before. So, let's say, just in a simple example, that if it's cold or wintertime and the outside temperature is below a certain level, maybe we wouldn't want the air conditioner to be on because it could damage the compressor . Perhaps there'll be a sensor circuit here that provides an input. And regardless of what any of the other inputs might say, if it's too cold out, it will never turn on the air conditioner. Another input might be is the engine overheating. If your engine's overheating, you're not gonna want the air conditioner on to put an extra load on the engine and make it overheat more so they will inhibit it. We're not allow the air conditioner to turn on if the circuit that is being monitored for the engine overheating is saying, Hey, this is too hot. Don't turn that a C on. Also, what if there's no request from the user? So if the A C is turned off, we definitely don't want the air conditioner on. There could be multiple inputs, but the module is programmed to analyze those inputs and then make a decision based on the programming that was put in from the factory. Now, even though this sounds a little bit complex, it's really not that much more difficult than diagnosing power, load and ground. The problem here is you have multiple power load and ground circuits. So if there were three different inputs, you would have three different power load and ground circuits if there was more than one output or if there was one out, but you would have one circuit. But if there was more than one, you would have more than one circuit over here, and then the module itself also requires power and ground, so you would have a number of circuits that you would have to check on before you would be able to decide where the fault is or which part of the system is at fault. Is it from the input side? Is it the module itself, or is it the output circuit? In the next video, we're gonna analyze a trunk release schematic, which is going to show us these three power load and ground circuits. We're gonna have the information circuit, the module and decision making circuit, and then the output circuit, which will be the drunk release actuator. And once we do it in pictures and do the diagnosis a couple of times, you'll find that your understanding from the basic electrical lessons will easily apply to these lessons and allow you to diagnose this type of problem in the same fashion as we did in the first videos. 15. Video 14 Trunk Release Schematic Explained: in this lesson, we're gonna look at a typical trunk release schematic. This circuit is made up of several components. We have the trunk release switch. We have the body control module, the trunk relay, which is located in the fuse box. There's also a fuse that protects the trunk actuator circuit. We have the actuator itself, and then there's also the key, less entry module. There's two ways that the trunk could be open. One is by pressing the truck really switch, and the other one is if you have a key, less entry or remote control for your vehicle. Pressing the trunk release on the remote would send a digital signal to the BCM, and then the BCM would then activate its control circuit, which would turn on the relay, which would then turn the trunk X waiter on and popped the trunk. We have three power load and ground circuits that make up this complete schematic, and then we have that one additional path between the keel, a century module and the body control module. And that's not a power load and ground circuit that's actually a digital circuit where the two modules air talking to each other, almost like two computers would talk if you had them networked together at your home. So it's a digital signal, which follows different rules than the power loading ground we're learning in this course. But understanding that there is a signal between these two modules and knowing that the key less entry module is part of the circuit can help you with your diagnosis, as we'll see in a little while here, with the three power loading ground circuits that make up this schematic, we have the input circuit, which has the trunk release, which, and the body control module is monitoring. Like we learned in the information circuits lesson. It's monitoring the ground side of the resistor. This'll arrow over here is telling us that there's a meter inside the module that is monitoring the voltage after the resistor, and this resistor would be the load. So the voltage after the resistor. If we were looking at this circuit, there would be 12 volts all the way up to the tip of the switch. Like we learned in the prior couple videos, the BCM would see 12 volts when the switch is open, and then when that switch closes. There would be zero volts on that meter because now the load is using up the voltage and we now have a complete ground path here. So this trunk release switch when it's activated is giving the BCM a way of knowing that the switch is being pressed. The second circuit for this schematic is the B. C. M's output circuit to control a relay in this one, we have the relay as the load and then we have the power part of the circuit here. And then we have the ground path, which is always there. So the part that gets turned on and off in this circuit is the power side, as in the case of the 1st 1 the trunk release switch circuit. The part that's getting turned on and off is the ground side where power and loader always there and then we have circuit number three, which is the actuator circuit itself. We have power here, and the relay switch is actually completing the power path. And then we have the fuse for protection for the actuator circuit, and then the actuator itself is the load. The thing that we're trying to turn on Now, some cars will have the output of the body module. It's possible toe have that directly control and actuator. But in order to do that, you would need toe. Have a higher powered circuit inside the body module that could handle the current of the actuator by using the relay. And remember, back from earlier lessons of relay allows a low current circuit to control a high current circuit. Many manufacturers will have the BCM control the output of the relay coil, which will then turn on the higher current circuit for the actuator. And they do this just so that they could make the BCM wiring be smaller and so they can make the internal circuit board and circuitry of the BCM not need to handle as much current as it would take to power up the trunk. Release actuator in the next video. We're going to spend a few minutes like we did in some prior videos and highlight the three power load and ground circuits because this practice is essential to getting your understanding to where you can recognize this by just taking a quick look at the schematic , you'll start to see them in color, even if you don't have your highlighters with you. So let's move on to the next video 16. Video 15 Trunk Release Schematic Highlighted: in this lesson, I'd like you to try and highlight the schematic, the three power load and ground circuits with the three colors that we were using in a prior lesson. I would like to highlight orange, where you expect to measure 12 volts green, where you have a load that is using up the voltage and yellow where you expect to measure zero volts after a while. When I do schematics, I will Onley highlight the circuit when it's operating. But in the beginning, it's worthwhile, at least for the first few toe. Highlight them two ways. Highlight them in the off position and then highlight them in the on position. In the off position, you'll usually just use orange and yellow because there'll be no load using up the voltage so there won't be any green on the page. But when you highlight the on position, you would then be closing this switch, and then the load would be using up the voltage so you would have orange, green and yellow when you're doing your highlighting and this digital circuit here for the key less entry. There's no power loading ground involved here, so that does not need or get any highlighting. What I'd like you to do is if you have the three color highlighters that we've been using. And if you have access to a printer, print out a couple copies of this schematic that's available in The additional Resource is for this lesson and pause the video and try and highlight power load and ground like we did in a prior video, and then start the video up when you're done and we'll go over what it should look like and we'll see how you did. So pause the video and give it a try. Okay, so for circuit one, if you started highlighting the off position, you just goto where the source voltages for that particular circuit. In this case per circuit. One. It's right up here inside the BCN, and you take your orange highlighter and highlight from where it says 12 volts all the way down until you find the first open and the first open would be at the tip of the trunk release switch, so you should have orange highlighted all the way down through to the tip of the switch. And if you wanted a highlight where you expect zero. You would start at the ground for that particular circuit, and you would just work your way up until you reach the first open, which in this case, is at the other side of the switch circuit. One would just have orange and yellow, and it would have orange all the way down to the switch, and the yellow would be all the way up to the switch. When we get to circuit number two, we would do the same thing. You start at the 12 volt source. In this case, it's inside the BCM again, and you would just highlight orange down to the first Open. And that would be right over here, a very short distance to the tip of the switch that's inside the BCM and then for the yellow or the ground, or where you expect zero volts. You would start at the ground G 302 in this case, and you would just work your way up with your yellow highlighter until you reach the first Open. It would go all the way through the relay, Sahlin oId because it's not active right now because there's an open switch. There's no power being supplied to it, and the yellow would come all the way up to the tip of the switch. So if you can remember this method of highlighting when you have the circuit off, it's really very easy. You find the ground path for that particular circuit and the power side for that particular circuit and just highlight until you reach the first open. So let's do circuit three. The 12 volts is coming from up here, so I'm going to start my orange highlighter and go down to the first Open. In this case, it's inside the relay switch and then for the ground side or the zero volt expectation, I'm going to start a G 302 again, and this time we're gonna work up the right side of the picture through the actuator, which isn't using up any voltage yet. And we come all the way up to the tip of the switch so there would be yellow all the way up to here. So take a look at your picture and see how you did. Once you do a few of these, you'll realize that you're really just doing orange and yellow, and you're starting at either the power or the ground and highlighting until you reach the first Open. Now, if there were multiple switches in Siris in one of these circuits, you would only have the yellow up to the first Open and you would only have the orange down to the first open. There could be part of the circuit that doesn't get highlighted in the off position because there might be multiple switches in Siris. But in this example, the whole circuit is being highlighted in either orange or yellow. So let's move on to having the circuit in operation and see what the highlighting would look like if I was to close the trunk release switch. Then I now have the power up here. I have the load, which is right here, And now that there's a ground path, it's going to be using up the voltage. So the easiest way to do the highlighting when the circuits on is to find the load that's active first and color that in green. So if this is the active load, when the switch is closed, you would just highlight Green right here on the resistor, and then, in order to figure out what to highlight in Orange and went to highlight in yellow everything from the load back to the 12 volt source would be orange. In this case, it's on Lee. This small amount that's inside the BCM and everything that's from the ground side of the active load all the way down to the ground would be yellow. So in this case, we would have this whole line all the way down through the switch. That would be yellow. So now let's look at circuit number two. You go about it the same way you find the load that's going to be active when the switch is closed. So when this which is closed inside the BCN, I now have the relay coil, which will be the load that's activated. So I would highlight the load in green just in here. Just this side you wouldn't color in the whole relay, because this relay actually belongs to two circuits and their separate. This dashed line is just meaning that the magnetic field is going to pull this switch over . There is no connection through this dashed line between on the inside of the really. It's just signifying that the magnetic field of the relay is going to pull the switch closed. So if I highlight the green for the relay coil, then everything from the power side of the relay coil back to the 12 volts is gonna be highlighted in orange. And everything from the ground side of the relay coil highlighted down to G 302 would be highlighted in yellow. And let's do circuit number three the same way. The glow that's going to be using up the voltage here is going to be the trunk release actuator. So this would be green right here and then everything from the power side of the load all the way back through the trunk release relay switch, which is now closed because the other circuits activated. It would be orange all the way back up through there, and then the yellow would be everything from the ground side of the load down to the ground . So, as you can see the same, the same principles get used over and over again. If you're highlighting the circuit in the off position or if you're highlighting the circuit in the on position and with a little practice on a few schematics, you'll find that you don't. You don't necessarily have to highlight every schematic because you'll see it. You'll understand it, even if you don't highlight it. Now if I find a complex schematic that I'm working on, that has mawr lines where they go around the page, where there's a lot of different pictures on the same page where I wanna have the wires that I'm looking at, stand out. I will still highlight schematics. But on a simple schematic like this, I may not do it as much anymore because I'm familiar with them enough where I can see the colors in my head just by looking at them. I see orange, green and yellow when I look at the page, even if it's in black and white. So as we move on to the next video, we're gonna practice, um, diagnosis and will create some faults and see if how we would work through using the diagnostic process that we learned in course, one in the beginner course how we can apply that to a more complex circuit and use some logical thinking to eliminate as much as we can. Before, we would even have to go to the car, and in some cases, like in the first course, you found that you could eliminate 50% 75% and sometimes even mawr of the circuit just by trying toe operate and finding out what parts of the circuit are functioning and what are not. So let's move on to the next video. 17. Video 16 Trunk Release Schematic Fault 1: Now let's use what we've learned and diagnose some potential problems with this particular circuit. Let's say the customer comes in or on your own car. You have a condition where the trunk release does not work. You press the drunk release switch and the drunk release actuator doesn't work. It doesn't pop the trunk, and you need to know where their start. So the place to start is to decide well, which circuit circuit one circuit to or circuit three is not functioning. And if you had a fall in circuit number one, is there a way you contest if circuit two and three or working without too much trouble Now , from your understanding of the description and operation of how this circuit works, you do have a remote on your vehicle where if you press the trunk, release on the remote, which sends a signal to the key less entry module, which then sends a signal to the body control module, which then activates the trunk release. If pressing the remote works and then the trunk release actually toe works, then what you've done is you've eliminated circuit number two from being at fault and circuit number three from being at fault. And you know that the problem on this particular car in this case is somewhere in circuit number one. Now, does that mean that it has to be the trump really switch? Just because you're pressing a switch? A lot of people, just because they press a switch and it doesn't work, they'll automatically say the switch is bad. But that doesn't have to be the case. What if this wire was open between the body control module and the trump Really switch for what? If the ground wire between the trunk release switch to the ground was open? Or what if the BCM internally had a fault where this resistor inside was opened and there was no path to be completed where the BCM could then know that it's being asked to activate the trunk? Relate. So what we do have is we have eliminated circuit two and three, as I said before, But what we now have to do is test circuit number one. And if you were going to do that on a car, the best place to test this circuit would be if you could simulate what the BCM or body control module would want to see in order to activate the relay. So realizing that this is a ground side switch and that this meter that's inside the BCM when it sees 12 volts, it thinks the switches open. And when it sees zero volts, it thinks the switch is closed. So what if you had a meter and you put it either at this terminal A here on the output of the BCN or if you put it at terminal nine on the power side of the switch? If you had a volt meter and hooked it from here to ground, then you should actually see 12 volts on that meter. Let's say it was easier to get to the location of the trunk release switch when you're done . When you when you're actually doing the diagnosis on a car, you look for where could you make your measurement? And then you look at where is the easiest location to get to? So if I could put a meter either here or here and if I measured 12 when I put my meter at location number nine here, pin nine of the truck really switch. If I got 12 when I pressed the switch, then that would mean that the switch or the ground path is not complete if it stays 12. When I pressed the switch, my fault is either going to be the trunk really switch or the ground. And how could I eliminate if it's the trunk release, which or the ground? Once I know that I have 12 volts here at Terminal number nine, then I know it's either the switch or the ground. But how could I eliminate which of the other two it is now? One way you could do it is disconnecting the switch and taking a jumper wire and just connecting your jumper wire between Terminal nine and Terminal eight. Because all you would be doing is using your jumper wire to simulate what the switch does. And you're actually using a makeshift switch, which in this case is your jumper wire to bypass what the trunk release, which does just so you contest it to decide if it's to switch or the ground. And if you put the jumper wire between Terminal nine and Terminal eight and the trunk release than activates, then you know what your fault is. You need a new trunk release, which, but if you were to put that same jump war between nine and eight and it did not activate, then that would mean that you have vault in the ground path and then you would have to try and locate where that fault waas. And in order to do that, sometimes that can be a harder thing to do on the car, because, let's say the trunk release switches in the dash, and then you would need to find the location of this ground on the car and you would have toe hunt for where the open in the ground might be now. Fortunately, most of the time the failure on some of these things will be the switch or the relay or the actuator. And when it's a component failure like that, it's much easier to narrow down and hunt and find the problem when you're doing your diagnosis on the schematic. If it turns out that it's gonna be a break in the wire in the harness that's going between the dash and the back of the car or wherever it is, then some of those issues are best left to somebody who's trained in doing that, so it's much harder to do something like that if you're new at it. The diagnostic practice that I'm trying to teach you in this course is to get you to understand where the faults might be. And you would still need to have quite a bit of on car experience if you were going to tackle looking for where the open might be in this particular circuit if it turned out to be the ground. And that doesn't mean that you can't do it because with a little practice, as long as you're careful and you get some basic hands on skills and then you get comfortable enough where you feel you're ready to try, then then it's worth doing. But this course is mostly the theory of the diagnostic process and given you a way to understand how to quickly narrow down enough of the circuits so that either you will be able to find the faulty component and replace it, or at least know what you need and have someone replace it for you or narrow down the possibilities so that you're aware of what may be your car may or may not need. So when you bring it to a service center, you won't get taken advantage of. So one last thought on this particular problem. What if you had your volt meter at position number nine here and you had your meter connected between pin nine and ground of the trunk release switch? And you were expecting to measure 12 volts before you hit the switch? But you only got zero. You got zero volts here. What would allow you to get zero volts here if this switch was not pressed? And then what if you went back here and made a measurement at Terminal A and you got 12 volts when you measure to Terminal A. But you got zero volts when you measure the Terminal nine. Well, you guessed it. That's telling you that there's an open beat in the wire between the body control module and the trunk release switch and again. Then you would have to go looking for where that open might be, and sometimes you can easily find it. And sometimes it's much trickier, like I was describing before, But at least we've narrowed it down to circuit number one. And in many, many more cases than not. It's just gonna be a trunk release switch if the fault is in circuit number one. So in the next video, we'll look at a different fault and we'll try and diagnose it the same way and the repetition that we're doing. We're picking on a few different schematics in the course, and we're going to analyze them several different ways in several different times with different faults. Because if you can get a strong understanding of a few circuits, then it's much easier to relate that strong understanding and apply it to circuits that you've not seen before. In my years of teaching, I've found that detailed analysis of a few circuits has given my students a much better understanding of electrical and has given them away toe. Apply what they've learned in that detailed explanation. Two circuits they've never seen before, and then they can still become comfortable with them. So that's why, in this course, and when I'm teaching, we do it that way because there's no way that you could learn every system, every schematic for every model car for every model year. There are just way too many models, pictures, different ways of drawing the same picture. You need to really understand what you're seeing on the page so that you can then go look for that on any picture. So let's move on to the next fault in the next video. 18. Video 17 Trunk Release Schematic Fault 2: welcome back. In this second fault, the complaint is the same as it was in the 1st 1 where the drunk release does not work. But in this case, the fault is different. The first step would be to operate the trunk release and see what happens. And when you press the drunk, really switch the trunk Actuator does not release. And then, if you had the remote for the car as well, and you press the trunk release on the remote, we would expect it to send a signal to the key less entry module, which would then tell the BCM Hey, we want to relate to be activated. And when you hit that, the trunk release also does not activate, and the drunk does not pop up. The next step would be to listen carefully and see if, when you were pressing the trunk release switch, do you hear the relay make a clicking sound? And this is a very important part that could be a huge time saver. So you want to be in a quiet area, press the trunk release switch and listen for a click, because if you get a click, it means that the relay coil circuit activated, and it means that it pulled the switch over to make a noise. It doesn't necessarily mean that the switch is making good contact with the other terminal of the switch, but it does mean that the magnet circuit worked and at least pulled something over to make the noise, the clicking noise. So what would that tell us if we have three circuits here? Circuit one circuit to and circuit three the actuator circuit if we actually hear a clicking noise when we press the Trump release? Which doesn't that mean that the trunk release which circuit one had to operate properly, and then doesn't it also mean that circuit to has to have been operating properly? So we've eliminated 2/3 of the circuit just by listening for the click. And now, because of that, all we have to do is diagnose circuit three. So where would you start? You would look at the picture and say, OK, well, where these components located, what's the easiest place to get to? If I wanted to make a measurement of some kind, and for a trunk release circuit, you can usually with your key, open the trunk and then look at the actuator up on the upper portion of the trunk and there's a couple terminals to it. And if you had access to these terminals with your meter, you could then see if you're getting voltage down to Terminal four of the trunk actuator. And if you're making this measurement, you would put your volt meter. Your red lead would go to Terminal four, and the black lead would go to ground. And we're doing what's called a voltage at measurement, where you're just trying to find out how much voltage is getting to terminal for. And if the relay switch did, in fact close, then you would expect that you would have 12 volts down a Terminal four. And if you look back at your highlighted picture of circuit three, when it was in the on position, you would see that it's orange all the way up to Terminal four of the Trump release actuator, because that's telling you what bolted you expect there. So let's say in this case we made this measurement on the car and we're getting 12 volts a terminal for So what does that do? It tells me that I can now eliminate through the relay and all the way down to this point that I'm getting that voltage. A Terminal four. Now what do I have to remember to do when I'm making this test? I'm not making this test and just hooking up my meter. I have to remember to press the trunk release switch to activate the circuit, which will then activate the relay, which will allow the 12 volts to get down to Terminal four. Don't make a test like this without understanding what you have to do in order to get that voltage to be there on a normally working circuit. Because if in a step by step diagnosis, if you mess up on any one of the steps, then it's going to throw off what your next step might be. And you'll wind up with an incorrect diagnosis. So it's very important to pay attention to the detail of what I'm trying to do and what I've eliminated and what I still need to test. So once I have the 12 volts at Terminal four, I still need to decide. Is it the actuator, or is it the ground path? Now let me ask you something. Can it be G 302 disconnected? Is it possible for that to be disconnected in this case for the trunk release actuator to to be not working? And if you think about it, the answer is no. It can't be G 302 disconnected. And why is that? The reason is because Circuit number two is working and circuit number two shares the same ground. So if I've measured 12 volts at Terminal four, then I know that my fault is either the actuator or the wire between pin number three of the actuator and this junction point of the grounds. And let's think for a second. How would I then eliminate which one of the problems it is? How would I make the next test or the next measurement to decide? Is it the actuator or is it the ground? And there's a couple ways you could do that. One way would be to take your meter and hook it up to pin number three. So if I put it at pin number three, I expect to measure zero volts at pin three when the circuit is off, and I also expect to measure zero volts at Penn three when the circuit is activated. Because if the circuit was working, this actuator would use up the voltage. However, if there was an open in this wire right here who are an open in this part of the wire over here, wouldn't that work just like when you have a circuit that's not working where you would have orange all the way up to the open? Even though there's a load in the picture, you would have orange through the load all the way up to the open, and then you would have yellow on the other side for zero. So if there was an open right over here, wouldn't I measured 12 volts when this is activated? When the relays on, Wouldn't I measure 12 volts all the way down through the actuator, up to the point where that open is located, making a measurement on the other side of the actuator with your volt meter from pin three to ground? If you were to measure 12 volts there when you press the trunk release, which that's telling you that the actuator is not open, it's telling you that the fault is in the ground path and that you haven't open now if you measured zero volts at Pin three but measured 12 volts at Pin four when you're pressing the trunk release switch now, those two readings would mean that the actuator itself is bad. So when diagnosing, we're trying to eliminate as many parts of the circuit is. We can just by activating the circuit and looking at the picture on how it's wired and what the components are and eliminating as much of the picture as we can and then make a test or two on the car if you have to, to eliminate the rest of the circuit. Now what if you don't want to work on your car yourself, but you don't mind doing the diagnostic part and the schematic part? What if you're less of a hands on person, but you're you like to do the thinking part, and you want to make sure that you've narrowed down some of the things that somebody might tell you you need. If you had this particular fault and you heard the relay click, you now realize that it's not the trunk release. Which circuit number two is also working if you brought it to a shop to have them check out your car for you. And they told you, well, you need a trump release switch. You would know that that's not the case because you're already hearing the really click. So for this fault, look at how much of the circuit was eliminated just by understanding that the relate clicking meant that Circuits one and two were both working and then meeting to make one or perhaps two tests to know what the problem is for this particular fall. So in the next video, let's look at a fault that involves the relay. 19. Video 18 Trunk Release Schematic Fault 3: So let's try one more fault. We have the Trump release not working again, but this time we have a different condition. The diagnostic process is gonna be the same, though. We're going to operate the trunk release switch and see what happens. In this case, we don't hear a click, and the trunk actuator also does not release. So the next step would be to take our remote if we have one available for the vehicle and press the drunk release on the remote. Because if the trunk release of the remote operates everything, then we know that our fault is in circuit number one, the trunk release switch circuit. But if the remote doesn't operate the Chua waiter, then we don't know if it's circuit number one or if it's circuit number two or if it's circuit number three. What if we don't hear a click? If we don't hear a click, that means it's either circuit one or two. But by not hearing the click, it pretty much eliminates circuit number three, because if the fault was in circuit number three, we would have had the response from the trunk release and from the switch and from the relay by getting the click, which would then have led us to number three. So by hearing no click, we can pretty much eliminate number three and start our diagnosis by finding out if circuit number one or circuit number two is working. And you can do this in a couple ways. Since you have to check both circuit number one and number two, you could start by making a test on circuit to, and if you got the right result, that would mean that circuit one had toe work. So, for example, let me explain what I mean. I could test circuit one first and hook my meter up to either point a to ground or terminal number nine to ground and look for the 12 volts on that wire to change to zero when I press the switch. And if I got that, that would tell me that Circuit number one is working. But I could also start my diagnosis on circuit to and perhaps make a measurement, either here at Terminal C or at Terminal 86 of the relay, whichever I could access more easily. And if I could access terminal D of the fuse block as well. That location would also work because anywhere on this wire, either a terminal C or terminal D of the fuse block or at terminal 86 of the relay. When I pressed the drunk release switch, I would expect that the BCM would close its internal switch and then supply 12 volts, which would then be available at any of those three locations if it was functioning properly. So if I made my test at Terminal D, for example, and I get 12 volts when I press this trunk release, which isn't that telling me that Circuit one had toe work and that circuit to is now good all the way up to Terminal D, and I still need to test the rest of circuit, too. But by starting with circuit to that first test eliminated part of circuit to and all of circuit one where if I start with circuit one and eliminate circuit one, I still have to go to circuit to and make some tests on that. So when you're doing your diagnosis, you evaluate what the picture looks like, and what process could help you narrow things down in less steps because the more. You have to touch the car and disconnect things, the more you have a chance of breaking something, the more you have to touch the car. The more you have to find the exact location of old of the different terminals of everything before you make your test. It's definitely a time saver, and it's also a much better feeling to know that you're diagnosing the car mawr what you're thinking than with tearing things apart in swapping parts and replacing everything to see if it works. And that's what a lot of people do that do it yourself. They'll say, Hey, my trunk least don't work Well, let me try our switch. Well, let me try an actuator. Well, I heard that maybe it's the relay. So then we'll somebody I know had one where the BCM wasn't working and then they just go through a cycle of putting parts in. And in some cases, if it's a common problem where so many cars are having the same problem, doing something like this may seem like it's a benefit to you. But in so many other cases, people will replace 123 parts, and it's just not normal for the car to need all of that. And if you get some education on what to do and how to make a few simple tests, then you can save an awful lot of money at an awful lot of time. And even if you're having someone else work on the car, you'll have enough knowledge to know what parts are possibly wrong or what parts you know can't be the problem in this case so that you can talk to them with a lot of education behind what you're saying so that you get the car fixed for the least amount of cost. So in this case, if I made a test at Terminal D and I got 12 volts, then that would mean that this switch operated. But if I got 12 volts here but still didn't get a click, maybe I have an issue with the relay itself or with this ground wire coming down here. If I wanted to find out if the relay was actually working, if I had a way of hooking my meter up either to Terminal 85 year or if I hooked my meter up to Terminal E if I was a terminal D, and I measured 12. How much should I measure at Terminal E if the relays working? If I press this switch and power is applied here and look back at your power on circuit schematic that you highlighted and when this circuit is on, you expect to measure zero a terminal E, and you expect to measure 12 at Terminal D. So if you measure 12 a Terminal D and also measured 12 at Terminal E. What does that mean? It means that the relay coil didn't use up the voltage because you now have some type of an open somewhere between Terminal E and the ground. That's what it's telling you. And if you measured zero a Terminal E but 12 a terminal D, then that means it's either a problem in the wiring that's internal inside the fuse block or the relay itself is bad. Now some of you might say, Well, can I just swap out a drunk relay with another relay on the car? And the answer is, of course you can. If you have a similar relay located right next to it that you want to use to swap as long as it's the same part. If you thought it was the relay, it doesn't hurt to change that. What I want you to understand is, how can I test the circuit? How can I narrow down things when I don't have some of that? There's nothing wrong with swapping a relay or swapping a bulb if that's what you think is easier. But where you have to be careful is I've watched so many people take apart a left side tail lamp assembly. They want to take it apart so that they can take the bull bat of that side and try it in the right side to see if it's the bowl and then when they take the left side apart, they damage part of the bump of facial, because when you're pulling the lens out, sometimes it scrapes along the bumper. Fisher and they were only taking that side out so that they could get the bulb to put in on the other side. The more things you take apart, the more you have a chance of breaking something, And if you're working in a shop on someone else's car and you break something on their car , that's on the other side of the car where you didn't even need to be. It's kind of showing that you don't know what you're doing, because there is a way of testing without having to borrow parts. Now, if you have a spare bulb readily available, and if you have a spare relay readily available and you don't have to do any kind of major disconnect or tear down to swap something out, by all means use that as part of your diagnosis. But when you don't have that availability, or if it's something that you don't want to damage or there's the potential for that, if you're gonna take that apart, make your tests be the simplest number of steps that you have to do. And that's what I'm trying to teach here. Your analysis and understanding of the picture and how the circuit works will eliminate, perhaps circuit one and circuit to what perhaps circuit to and circuit three or whatever it is so that the amount of testing you have to do on the car becomes one or two tests and then you'll know the answer. In the next video, we're gonna look a different schematic. We're gonna look at the cooling fans schematic. And this particular picture has five different power load and grounds, all working together to make the fan work at either low speed or high speed, and this circuit will give us a chance to enhance our skills even further. 20. Video 19 Coolant Fan Schematic Explained: our next dramatic is a cooling fan circuit that has five separate power load and ground circuits. The PCM controls the operation of the fans by closing one or both switches when it wants low speed operation. The PCM will close this switch over here. The low speed cooling fan relate control, and what that does is it allows there to be a power loading ground path through the relay through the switch to ground. So that's our first Circuit, Then the low speed operation circuit would be from our 12 volt supply here hot on all times through the fuse and threw the switch of the relay that's now closed through the right side fan. And then it comes to this fan control mode relay, and there's actually a path through this relay in the off position that will then allow that voltage to get over to the left side fan. And what happens is when when the PCM turns on that low speed thin, just activating that one relay relay one. The cooling fans are wired in series where they will be sharing the voltage if you remember back to Serie circuit discussion and when they share the voltage. They'll get approximately six fold each, which would then allow them to spend slower than normal. So they'll both beyond, but they'll both be spinning slow and one other note on the mode relay. This relay would be called a single pole double throw relay, and when they define relays toe have that type of designation. It just means that the input is one input and the outputs. There's two outputs that actually connect to things, so there's an output for the off position of the relay. And then there's an output for the on position of the relay. And if you compare that to the other two relays here, they're both what's called single pole single throw, meaning There's one input and one output, and you can see the same thing over here on fan control to relay one input and one output. But the middle relay here, the fan control mode relay is called single pole double throw because there's two positions or two outputs that actually complete electrical paths. There's our first to power loading ground circuits. Now we have a couple more when the high speed cooling fan circuit gets completed. When the PCM closes the high speed switch, it actually turns on both of the other two relays. So it's now providing a ground path for the fan control relate to and a ground path for the fan control mode relay. So we would have power going through the fuse coming through the relay coil to ground, and we would also have power coming through the fuse coming through the mod relay coil to ground. And when the high speed circuit has turned on in this particular application, the low speed is turned on first, and then a couple seconds later, the high speed is turned on, so it actually activates all three relays. And when all three relays are activated, we have relay one, which is on which is allowing 12 volts to get to Terminal A of the right side fan. But when the mod relay is pulled over and activated so that it's completing the pet to be six instead of be five, what happens now is the path through the right side. Cooling fan goes this way, and then it actually comes over to this junction point to ground when we have the high speed control on and both switches inside the PCM closed. The right side fan has its own path to ground, so it will be spinning at full speed or high speed and by closing fan control, relate to as well. What that does is it now allows this switch to be closed, which provides 12 volts directly to the left side fan, which is also connected to the same ground. So now I have the two separate fans spinning at high speed, which would provide much more additional cooling for the engine in this particular case. So we have quite a few power load and ground pats to consider. But the good news is by seeing what circuits are working and what circuits are not. For example, if low speed is working and high speed is not. If high speed is working and low speed is not, or whatever the scenario is, we will be able to eliminate parts of the picture because we know that those parts of the circuit of the parts that are operating normal have to be good. And when we get to the diagnosis part, I'll show you how much of a huge benefit that can be. The one other thing that we didn't talk about yet is when will the PCM close this switch? The low speed switch and when will it close the high speed switch for this particular car? The low speed fan will come on when the coolant temperature reaches about 215 to 217 degrees Fahrenheit and the high speed family come on. If the coolant reaches a temperature of about 230 degrees Fahrenheit, the PCM will also turn on the fans if the air conditioner is requested and certain pressures inside the A C system her exceeded. So if the A C is on and the high pressure exceeds a certain value, it'll turn on the low speed. And if the high pressure exceeds another value, it'll turn on the high speed because the air conditioner, in order to operate efficiently, requires good airflow through the condenser. So when the pressures get too high in the A C system, the fan needs to be turned on toe. Allow that airflow so that the A C can work properly. So while this schematic looks complicated at first, when you break it down into all of the power loan and ground circuits, and what we're going to do in the next video is will highlight power loading ground from low speed operation that will highlight power load and ground for high speed operation. And we'll start by doing the control side of the circuit, where we just highlight the circuit for the relay fan control one, which is the Onley relay that comes on for low speed. And then we will highlight the circuits for all three relays for high speed because all of them come on when high speed operation is requested. 21. Video 20 Coolant Fan Schematic Highlighted OFF: Welcome back in this video, we're gonna highlight the schematic in the off position. So if you haven't done so already, go to the additional Resource is and print out if you can the schematic and print a few copies. Because in the upcoming videos, we're gonna also highlight the fans in low speed and in high speed. And while this will take a little time to do, it is well worth the effort because the first few schematics that you do that air complex spending the time to highlight them will make it so much easier to understand. Because then, even if it's not highlighted, you'll look at the picture and you'll start to see the power load and ground sections as if they're lighting up for you. So pause the video and turn it back on one done, and we'll see how you did. Okay, if you remember in a prior video, we talked about how Teoh easily highlight a schematic in the off position by starting either at the power supply and going until you reach an open and coloring that an orange or starting at the ground whichever ground you're going to start, at which Teoh wanna one or the ground inside the PCM for high speed or the ground for low speed. In either case, we're going to start at those extreme locations either the grounds or the power supply side , and we're gonna highlight until we reach the first open. So let's do the power side first. So with an orange highlighter you would highlight from here down to this junction point. And first, let's start by going this way, and you would highlight up to the first Open, which would be this switch. But you would also expect to measure 12 volts all the way through this point to the tip of this switch, so there would be 12 volts available on all of those wires that are highlighted in orange. However, there's more because we have a path in this direction as well, and you should be highlighting orange all the way down to this point and then continuing over to the left and down through this relay coil and back to this junction point and then down to the tip of the switch inside the PCM. And there's still two other pets. We have the path here through and relate to which would come over to here, and this part's already highlighted so we don't need to do that again. And then we have our final full volt path, which comes over here up to the tip of fan relay twos switch. So all of that should be highlighted in orange in the off position because if we were to make measurements on the car in all of those positions, we would measure 12 volts if the circuit was working in all of those locations. So now let's do the ground side. We'll start with the two grounds inside the PCM because there's very little to do there. If I start here and I go up to the first Open, I'm just moving up a little bit inside the PCM and all that gets highlighted in yellow is this little tiny section and the same thing on the high speed cooling fans, which all that gets highlighted in yellow is this little tiny section up to the first Open . However, if I'm doing G 101 I would need to go quite a few directions. So let's start a G 101 and I would work my way up to this junction Point splice 148 And I would keep going straight up through the through the fan motor for the left side cooling fan up to inside the relay inside the fan control relay. I would also be highlighting and yellow in this direction here, up until I reach the first Open and the same thing here from Splice s 175 I would have to come over here until I reached the first Open. It would actually go through the mod, relate through the right side fan and up to this point. Now, you could also highlight in yellow these two paths over here, this ground distribution schematic. It just means that there are other devices that are using G 101 that are funneling down and using their ground path through to this same location. So since it doesn't really pertain to the cooling fan, it's optional. If you want to highlight that or not, but realize that that would be zero volts as well. So what I'd like you to do is put this picture aside. And in the next video, we're gonna highlight what the fans power load and ground picture would look like for low speed operation. And in this case, we're gonna need orange, green and yellow because we will have loads that are active in the off position. There were no active loads, so it was just orange and yellow for 12 volts and zero volts. So I'll see you in the next video. 22. Video 21 Coolant Fan Schematic Highlighted Low Speed: in this video, we're gonna highlight the low speed fan operation with three colors orange, green and yellow, where green will be the load that is active. Using a voltage orange will be 12 volts and zero volts will be represented with the yellow highlighting. So the best wave I've found toe identify how this should be highlighted when you're doing the on position is by starting at the loads that are gonna be active and then going from the power side of the load back to the voltage source and from the ground side of the load to the ground. In this case, we have the low speed relay that comes on to power up the right side cooling fan and then complete a series circuit through the left side, cooling fan to ground. So our first load that will be highlighted in green is the relay coil for fan control. Relay one. And then what we will do is from the power side of that relay coil. We're going to use orange to follow our path back to the voltage source, which is up here where it says hot at all times. Then we'll do the zero volts side by going to the ground side of the relay coil and highlighting yellow from there all the way down through the now closed switch to ground. So that's our first completed path, highlighted in orange, green and yellow from here from hot at all times through the relay coil to ground. And remember that the low speed cooling fan control switch gets turned on inside the PCM to activate the low speed circuit. And once we do have that circuit activated this switch for fan control Relay one is gonna get pulled over to complete the path to allow power to get to our second active load here, which will be the right side fan. So I'm gonna color this load in green. But since I have a series circuit that goes through to another load over here, I'm gonna also color this fan in green. And I'm going to color the wiring in between the two fans in green as well, because those air representing a voltage that is less than 12 volts but more than zero volts. Because since the two fans are going to share the 12 volts, you will wind up with close to six volts on this wire in between the two fans when it's on low speed. I like to highlight that wire in green because that's part of the loads that are actually using up the voltage. Now some people, some of my students, like to highlight that as a dash line because it's actually the wire is not really using the voltage except for that very small amount we talked about in the voltage drop section. But it's up to you if you want to highlight it as a solid line or is a dash line. But the green would go from Terminal A of the right side fan all the way through the mod relay to Terminal B of the left side fan. And then what we need to do is highlight the power side, which would be from Terminal A over here, up through the relay switch, which is closed, and back to the voltage source, where it says hot at all times here and then the ground side. What gets colored in yellow for the low speed picture is just this small section from Terminal B down to the ground. So you're going from the ground side of the load, which would be, after all of the loads and just highlight yellow or zero volts from Terminal B down to G 101 So now we have two pictures done, we have the off position and we have the low speed position. In the next video, we're going to highlight the on position. And as you'll see once we get started, it's going to cover most of the page in orange, green and yellow because all of the circuits are activated during high speed, so I'll see you in the next video. 23. Video 22 Coolant Fan Schematic Highlighted High Speed: in this video, we're gonna highlight high speed operation power loading ground using our three colors orange, green and yellow. And if you remember from the description for high speed, both switches inside the powertrain control module are activated so we can close both of those switches. And also, when we do close those switches, what that's going to do is it's gonna activate all three relays, so all three relays will have moved the switches. The fan relay one will close this switch fan relay to will close this switch, and the mode relay will actually switch over to its other connection at Terminal B six, which will then allow the fans to run at high speed. So if you haven't tried already paused video and color in using the three colors power load and ground, where you expect to measure 12 where you expect to measure zero and what the loads are that are using up the voltage. And in this case, all five loads are active loads, so all five of them the three relay coils end. The two fan motors will be colored in in green, so pause the video and started up again and will review what it should look like. Okay, we're back. So let's start by coloring in green all of the loads, and I can start with the fan motor, the right side cooling fan I concolor that green and the left side cooling fan that would also be green. And then I have really coil for fan control related one. And don't get in the habit of coloring in the whole box. Just color the electrical component because if you call it in the whole box for the relay, there's actually two paths there, and the only part of the path that should be green is the coil. So just color in green on the relay coil itself and then do the same thing for the fan control mode. Relay coil and the coil for fan control relate number two. So now what we have to do is start at the power side of each load, one at a time and then highlight in orange from that load back to the power source. So we'll start with thank control related ones coil and will highlight an orange from here all the way back to the power source, just like we did when it was low speed. And then we will highlight the right side cooling fan in orange from Terminal A all the way back through the relay switch to the power source. And since this wires already highlighted in orange from this junction point, I only have to go up to here. Now let's move over to the other two relays. We have the power side of the mod relay. We need to highlight that in orange and then up through the fuse to this junction point and then fan control relate to from Terminal B one here up to this point, which is already highlighted in orange so we can stop there. And then we have from the left side cooling fan, which has its own power source now, which is why it's going to spin faster. And we have high speed operation. We're gonna go from Terminal A up through fan control, relate to the switch is closed and up to this junction point, and then the rest is already highlighted in orange. So now we have the power part of the circuit and the load part of the circuit highlighted, and to do the ground. We're just going to start at the ground side of all of the loads and in yellow, we're gonna color the path down to ground so that we have our zero volt part of the circuit represented. So from the relay coil of fan control relay one, I'm gonna highlight yellow from the ground side of that coil all the way down through the close switch of the low speed cooling fan Relate Control. Then I'm gonna go to the right side cooling fan and from terminal B, we're gonna highlight in yellow. And we're gonna go through the switch that's now swung over to complete the pad to be six. And then we're gonna follow that to ground past splice s 1 48 and then down to G 101 And notice that the right side fan now has its own 12 volts. It has 12 volts at Terminal A, and there's zero volts at Terminal B because it's the only load in the circuit coming all the way through to ground. Next, we need the ground path. But the other two relays that are controlled by the high speed cooling fan relate control. So from the ground side or terminal C six here of the fan mode. Really? We're gonna go down through here, past this junction point and down to ground and the same thing for fan control relate to. We're going to start at the ground side of the relay coil and work our way down to the spice, and then the rest of that circuit is already highlighted, so we don't have to continue the rest of the way. And our last ground is gonna be for the left side cooling fan itself, which will start at the ground side of the load, which is terminal B and just color down through two G 101 And really, we only need to do this small section here because the rest of it's already highlighted from before. So if you look at these three pictures now that you've highlighted, the most important ones are the low speed in the high speed picture. In the future, we probably will not highlight the off position very often because it's not as necessary. If a picture is complex enough there there are some occasions where I might highlight the off position, but for most times I will just highlight the on position or the low speed in the hyper speed position, especially if the circuit or schematic is complicated. In the next video, we can use these pictures to diagnose some faults in the cooling fan circuit, so let's move on to the next video and see if you're up to the challenge. 24. Video 23 Coolant Fan Fault Low Speed INOP: in this video, we're gonna be diagnosing a situation where both low speed fans do not work. But the high speed fans do work now if you think about it a second, how many customers, if you were working in a shop, would actually come in and tell you that the low speed fan works where the low speed fan doesn't work and the high speed fan does work? They would come in with some other type of a complaint. So since it's the job of the low speed fans to come on, when coolant reaches a certain low threshold temperature, and then if it gets hotter than the high speed fans come on when reaches that second threshold temperature. So the complaint from the customer could be one of a couple of things. They might complain that their temp gauges going up higher than it used to because the low speed fans air not coming on it all. And the gauge just keeps going up until it reaches that second threshold temperature, and then the high speed fans do come on so there wouldn't be an overheating condition. It would just be a condition where the temp gauges going up higher than normal now. The other thing that somebody might say is that their engine is noisy or their fans are making more noise than they usually do. And this could be the same thing, meaning that the low speed fans air not working because normally in most situations, the low speed fans have enough capacity to do the job to maintain the engine coolant at the temperature that they need. However, if you're on a hot day or in a hot climate and you're sitting in traffic where you're not getting the airflow through the radiator from just the car moving, then the high speed fans air needed to give that extra boost of cooling capacity so that the engine condone release its heat. So the type of complaint you would get would be usually one of those two things. Either the gauges going up too high or my fans are making more noise or there is extra noise in the engine and I don't know what it is, but not really an overheating complaint, and some people actually who understand their cars more. They may look into it a little and say, you know, I'm not seeing my fans come on for low speed, but then they're coming on on high speed so you could get any of those situations. But how you would diagnosis it is actually easy. If you understand the picture now, looking at this blank picture that's not highlighted, it looks like, Well, where do you start? You need to know what the low speed fan uses on this schematic in order for it to operate. So we could look at a low speed picture for a second and we could say Alright if low speeds not working something must be wrong with one part of the circuit that's highlighted in the low speed picture. So we do have to power load and ground pets. We have the path from hot at all times that powers up the relay itself, and then the powertrain control module completes the ground path for the relate, which then closes over this switch, which then allow is both fans to be connected in series, and then this other ground path over here, G 101 is always there as a ground. We know that the fault needs to be somewhere along one of these pants and it could be in this wire. It could be in this wire. It could be in this wire. It could be a fan itself if you do a little deductive reasoning and think, Well, wait a second. There are some things I know. I know that the high speed fan works. So if both fans air coming on properly in high speed, then my fault is not with this fan. My fault is not with this ground. My fault is not with this fan. And it's not even with this wire. It's not with this wire. So the way would go about this is look at what has to be good and eliminate as much as you can before you even start to diagnose. Well, could it be this? Could it be that Could it be that so let's look at the high speed picture and look at how much has to be good on this particular circuit. So here I have the high speed picture that has five power load and ground pants. I have the path through each of the relays over here and over here. Then I have the path through the fan. One would be through this fan over here, which now has its own ground on high speed, and the other would be through the relay here, which has its own ground on high speed. What I know if high speed is working for both fans, is that all of what I'm looking at that's colored in has to be good, meaning the PCM is doing its job in order for high speed to work, the PCM must be closing this switch. Otherwise it wouldn't be operating the left side cooling fame. It wouldn't allow the right side cooling fan to have its own ground if this relay didn't work. And what if it was the low speed switch that didn't work? If this never turned on, I would never have power to the right side fan. So since the right side fan is also coming on in high but not coming on and low, then it can't be this path to ground over here, either. The fault has to be in something that's not highlighted, and in this particular case it's very easy to see that the fault has to be either. In the switch of this relay, the contact here for the off position of the relay or in this wire that goes up from here to here. And if I switch back to the low speed fan and we now look at that wire, the fault has to be either this relay or this wire, and that's all it can be. And this is just by understanding the condition. So we have narrowed down this fall to be something very small on a complex picture without doing too much work other than understanding the circuit. So let's say we actually had this condition. How would I then eliminate if it's the relate, the contact in the relay or the wire? If I was to test this on the car one way, I can do it without even having the fans have to get up to operating temperature again because sometimes, depending on the temperature of the day, it may be difficult to get the high speed fans to come on. You'd have to leave the hood close or block airflow to allow it to get up to the temperature needed to get the fans on high to try to test the system a little bit. But what you could do is once you know that the fans work on high and you know that this relay is good and you're just trying to find out if the problem is in this relay contact or in this wire. What you can do is even with the engine cool, you can find these three relays in the under Hood Junction block. I would remove this relay fan control Relay one, and I would put a jumper wire from Terminal C eight to Terminal B 10 on the car with the relate removed so that I'm completing this path without having to turn the fans on. And then what I would do is remove fan control mode relay. Just pull it out of the fuse box and then use another jumper wire to go from Terminal C four to Terminal B five. So what we're essentially doing is with everything off, and you can even do this with the engine off because this is hot at all times. If I was to pull out these two relays and put a jumper wire from here to here, all that's doing is completing this past so the fan will be on low speed, or it would be commanding low speed, and then I'm completing this path to tell if it was the relate or the wire. And when I do this test, if the fans turn on when I put my jumper wire here and remember, I still need to have this first jumper wire here so that the power actually gets over to fan control mode relay. But when I put this second jumper wire in, if the fans come on, then that means the problem was the relay. Because if the problem was in this wire, even with the Jumper wire here, it still wouldn't work because there would be an open somewhere in the wire in between this point and this point. So it really comes down to a very simple test if you wanted to do this on the car. But the best part is, even if you don't want to do any of the on car work or you're not comfortable with jumper wires and relays, which would be more of an advanced topic. But because you do have to be comfortable with either using the jumper wires or identifying the correct relay and making sure that you're hitting the right terminals when you're doing the jumper. So if you're not comfortable with that part, you can still do the diagnosis part and eliminate most of this picture toe where you know it's either gonna be the relay or the wire. So could you also just substitute a known good relay from one of the other locations on the car and see if low speed works? And if you could find another single pole double throw relay on your car, that's the same type and just unplugged that for a second and plug it in the place of this one and then the if low speed fans come on. If low speed fans come on, then you know it was the relay and a flow. Speed fans, and do not come on. Then you know it's the wire, and if it is the wire, you will need further diagnosis into where the location is on the wire that the open is. But this course is not the hands on course. It's more of the diagnostic course to get you to understand the diagnostic process. If you decide that you want to pursue working on your car further than you would need to perhaps take a hands on course at an adult education place. Or you could look online where you could find some of the websites that post videos demonstrating how to do some of these repairs. One of the sites that I've found that does a good job at showing how to do some of the mechanical end of the repairs instead of diagnostic, which is what we're focused on here. The site is called chris fixed dot com c h r i S f i x e d dot com So if you look there, you can find some videos that will definitely benefit you in learning some of the hands on skills. You still have to get comfortable with doing what's being shown in some of those videos. But at least there are some avenues to go. If if you want toe pursue learning how to work on the car yourself. This course is focused on diagnostic, and it's trying to give you the information that you don't see in many other places. How to simplify the circuit, how to understand the circuit and how to make a diagnosis and eliminate all of the different possibilities and come down to what has to be wrong and what the few simple tests would have to be if you were doing the work yourself. So in this case, and in most cases it would be more common for the fall to be in the relay than it would to be in the wire. But again, it could be either one. And you would still have to make a diagnosis to make a decision on if it was the relay or the wire in the next video. We're gonna look at a situation where low speed works, but high speed doesn't work, and we're gonna go through the same process and see if we can narrow things down relatively quickly again. 25. Video 24 Coolant Fan Fault High Speed INOP: in this video, The fault is gonna be that the high speed cooling fans don't work. But this time the low speed fans do. We're now. The complaint in this case would be something along the lines of my car overheats, but only on a hot day, or only when I'm in heavy traffic. And the reason for that is the low speed fans air coming on and doing the job most of the time, but one that extra cooling is needed, then the high speed fans are not coming on and not giving that extra amount of cooling necessary to bring the engine back to the temperature it needs to be. And in many cases, if it was winter time or even spring and fall in some places, this high speed fan could not be working for months and they wouldn't even know it. But when they do finally need the high speed fan toe work and the car starts to overheat in high temperature or in heavy traffic, then we would need to know what to do and we're going to go about it in the same fashion as we did with the last fall by trying to deduce what it could be based on what we know about how low speed fans work and how high speed fans work, and eliminating the parts of the picture that we can and then reasoning out where the fault would have to be in order to cause the situation that we have on the vehicle. So in this case, the low speed fan works, but the high speed fan does not. So let's take a look at the low speed fan picture and identify what has to be good. So here I have the low speed picture highlighted, and what I'm doing now is I'm realizing that everything that's highlighted right now on this page cannot be the fault, because in order for low speed to work properly, all of these wires and components need to be functioning properly. So that means my next step would be to decide what that is not highlighted. What's left could cause both high speed fans to not work because there were some of these wires that are left, which may only cause one of them to not work, but which one would cause both high speed fans not work, because none of the fans air coming on in high speed. So what we're gonna do is just look at all of the remaining wires and this is without going to the car other than to confirm that low speed worked and high speed does not come on. So if there was a fault with this relay over here, the fan mode relay or for that matter, if there was a fault with this wire that goes from this location over to the mod relay and all the way back to this junction point, if there was a fault in any of this part of the circuit, would it cause both fans not to work? And the answer is no. If there was a fault here, I would still have this relay functioning when the high speed cooling fan really control turned on. And then this relay would turn on and this fan would come on high because it would have its own power source now. So when you're diagnosing electrical, your starting point of diagnosis is always assuming that there's only one fault until you realize that there has to be more than one when there's more than one. Most often it's caused by having the existing fault and then somebody working on the car and leaving something disconnected or something that they broke while they were trying to check the original fall. But for most cases, there's only gonna be one fault that can cause the issue. And if it turns out that it's, too, you're just going to diagnose it as far as you can, assuming that it's one fault. And then something in your diagnosis will show that there has to be a second fault in order to cause this condition. But for now, we're gonna assume that there's only one fault and we haven't brought it anywhere for somebody to damage something. And we're just looking for the one cause that could cause both fans not to work. So I can actually eliminate this wire because that would not cause both fans not toe work. And if you think about it, I can also eliminate this wire and this relay coil up to this point as well, because if the fault was over here, then there would still be a path through this relay to ground when this high speed cooling fan relate control came on, and if there Waas. What would happen is when the temperature got hot enough, this switch would close. And this fan, which was sharing the voltage with the fan over here, would now switch over to have its own ground and it would come on high. So the condition would not be that the fans don't Come on. Hi. The condition there would be that when it gets too high speed on Lee, the right side fan comes on high and the left side doesn't. And in many more cases, it would be enough cooling capacity to have the car not have any issue or complaint at all . So since this wire and this relay coil and this wire would not cause both cooling fans not to work on high, we can eliminate that as well. And we can even eliminate this path on this side over here because if the problem was in the relay switch or in this wire over here from this junction, point over to the switch or from the other side of the switch down to Junction Point s 1 75 If the problem was over there, I would have the same situation where the left side fan would not be able to power on high , but the right side fan would because this relay would activate, pull the switch over and give a ground path to the right side fan so that it would spin on high speed. I've eliminated a good part of the circuit just by realizing that all of these other wires could not cause both fans not to work. And what we have left is just two things. We have this path from this junction point down to the powertrain control module, including the module itself. Maybe the switch inside his bed. So it could be that this wire is no good. And it could be that the powertrain control module is not closing this switch. But it also could be one other thing. What if this fuse was blown or anywhere between this junction point and here, but also this little section of wire inside the fuse box itself? So the fault would need to be in order for high speed, not toe work. But low speed work fault would have to be between here and here or between here and here. What you're doing is we've sat down and just reasoned out once you confirmed that high speed doesn't work and low speed does work. Or if you just heard that that's the condition from your driving or somebody told you that that's what's going on. You could sit down with the pictures and highlight them and then look at what it could be and narrow it down to just those two locations. And then you could even advise somebody. Well, you might want to check the fuse, the 25 amp. Fuse that powers up, then relay controlled, too, because in many cases you might find that that's the fall. It could also be in the wire, like I showed over here between this spice location and the powertrain control module. Now, if you were gonna check this on a car just to give you a way to go, If you are one of the hands on people that want to do some of the work yourself, what you would do is just put a volt meter or a test light at one of these locations. Check the fuse itself by looking for 12 volts here, or check for 12 volts at this location. If I get 12 volts at C one or the best place to check would be at B one or B four. Because if I check it, be one or before I'm not only checking the fuse. I'm also checking this other little section of wire where, if I check at C one, I would be finding out that the fuse is good, but it wouldn't eliminate this little piece of wire right here. But if I made my first test on the car at either be one or before then, I would know that this one area that could be at fault is no longer the problem. And even if I just check the fuse itself, it would eliminate the fuse. But it wouldn't eliminate this area right here. My first test might be it. Be one or before if it was easy to get to. And now there's nothing wrong with checking the fuse first and then going to be one. And before, in many cases, that's a much easier way to go. But if it's easy to get to before, I might make the one test right here, because that would eliminate this whole amount of wire right here from being the fault if I still had the issue after I tested that and wanted to make a determination of if it was the powertrain control module or this wire, One of the ways I would do this if I was working on the vehicle is to provide a jumper wire to ground right at this location. And what that does is it gives a ground to the wire instead of the PCM giving the ground to the wire. And if I did put a ground wire from here to ground from Terminal five on connector see one at the powertrain control module. If I put a ground there, what I would get is if the wire was bad, it would not turn on these relays. And if the wire was good, then it would turn on the relays. And it would suggest that the powertrain control module is not doing its job turning on the high speed fan. And if it did come to that, where was the powertrain control module? As the Onley culprit left? There is one other thing that you need to do before you would replace the powertrain control module you would need to know from the description and operation. What is the temperature that it is looking for before will close this switch and make sure that the temperature of the coolant or the signal from the temperature sensor, which we're going to talk about in a little bit, make sure that that signal is giving a temperature That's high enough, allowing this to do its job. Because if you were to replace the powertrain control module and the temperature sensor circuit had an issue where it was never providing a signal for the high speed fan to work, then you would be replacing the PCM, and it would still do the same thing. So we would definitely need to verify that the car has reached the proper temperature. Now, if you have a scan tool, which is used in a shop, this becomes very easy, and we're gonna talk about scan tool considerations in another lesson. But if you had a scanner, you could monitor the temperature of the coolant and make sure that it achieved that level . And if it did, and then the PCM still did not turn that switch on, then you would know that the PCM is not doing its job And once again this is after you eliminated this wire and the fuse and this other section of wire here without a scanner, the only recourse that you have is making sure that the coolant gets hot enough, perhaps by putting the thermometer in the radiator with the cap off. And it would take a long time for it to get up to temperature, because you're not allowing the pressure cap to be on. So it's certain things. If you don't have a scanner to monitor, some of these items would be difficult to do on your own. But again, the purpose of this course is to allow you to narrow down so much of the circuit so that you have an idea of where the fault is, or that one or two or three possible things that it could be and then make a decision on how you want to proceed. For some people, it might be well, if one of the possibilities is a relay. Maybe I'll just change that relay and see if I can take care of that. And then if it becomes something where it needs to be investigated further, where it could be a PCM where this wire. Maybe I'll bring it to a shop for that part. But all at least no, that if they start telling me that my fan is no good or if it could be this relay or that, really, I'll know that they're really not understanding the circuit, and I may want to bring my car elsewhere. If I'm getting information from them that corresponds to something that it can't possibly be in the next lesson, we'll talk a little bit about what a shop would do, or if you had your own scan tool that was capable of turning on the different switches in the powertrain control module. How it would make your life a little bit easier if you had that. And it doesn't mean that you can't diagnose the picture without it. But there's no denying that having a scanner and knowing how to use it to monitor the different switches and areas of the circuit and make commands to turn on low speed or Tony turn on high speed. How this would be an advantage if you were working, especially in a shop, or if you were working on your own car more often, it might be worth the cost of a scanner, so we'll look into that a little bit in the next video. 26. Video 25 A Little Bit About Scanners: in this video, I want to talk a little bit about scan tools and how they can help you were aid in your diagnosis and for most do it yourselfers. It's not worth the investment of paying the $1000 much, much more for a sophisticated scan tool that has what's called bi directional capability. The ability to turn on different devices and control the different modules on your car and either monitor all of the switches that they're controlling or monitoring or monitoring the outputs, or even being able to turn them on for the different modules on the car. Scanners like that can cost thousands of dollars. And even if you spend thousands of dollars, you may not get all of the capabilities that the factory scanner would have if you were buying the one made by the manufacturer or recommended by the manufacturer for your particular car. So there's a vast amount of different types of scanners that are out there, and some people will call code readers, which just read the trouble code that's on your engine computer. Some people even consider those as scanners because it's scanning the computer of the car to find out if there's any trouble codes and you'll see ads on TV saying how this is the next best thing since sliced bread, where it's gonna tell you what's wrong with your car and toe a point. It does give you some information, but does it tell you what's wrong with your car? In most cases? No, it will tell you what the code is, which could be a help, but it will not give you the diagnostic or the testing that's necessary after that to make sure that it is either the center of the wire or the module or something else. So right now I'm on Amazon, and I did a quick search for automotive scanners just to see what it would bring up to show you how many different ones air available out there. And if I scroll down, you can see that the pricing can range anywhere from $100 less than $100 thousands of dollars. And there are pages and pages of these, and in my career, I've used most often the factory scanner or a high end aftermarket scanner, and I would not have any details for you on any of these thousands of scanners that are available out there right now. But what I can tell you that is, if you're looking for a code reader, you look for recommendations from people that have bought the product and see if it has what you're looking for, and then try and make the best decision that you can and the same thing when you're choosing the scanner. If you're choosing a lower end one if you need one that is just gonna allow you to read the data from a certain module, maybe the engine computer and maybe the body computer than you would pay a lot less than if you're tryingto have a bi directional scanner that can also turn things on and read anti lock brake modules and airbag modules and all those other modules the more you want to do with your scanner them or you're gonna have to pay for it. And as you try to make that decision, base it on how much you're gonna work on your car and how much you think you need it. In this course, I'm just trying to get you the information for how to use the schematics and the diagnostics of them and the scanner condemn finitely. Be helpful for some of those, but there are so many things and so many ways you can narrow down what could be wrong with your car without having one? Will it take a little more time? Yes, but is it possible to narrow down many of the things that it cannot be and have a couple things left where then you can either borrow a scan tool or bring it to a shop and have them do the rest of the work. Or at least you know where the area is that your car needs repair, and it will help you not get taken advantage of if you're. If you're doing this extra diagnostic, work yourself and it will also help you save money from just swapping parts, which most people do. They'll just say, Well, it could be this. It could be that I heard it was this on one car, and they just start swapping parts. So in this course I'm trying to give you as much as I can of how to diagnose the car as if you didn't have the scanner. But I wanted to provide this additional information just to show you that it does open some more doors having the additional tools, especially if you have one of the high end ones that can command things on and off and monitor all the different switches. So now, if I come back to the schematic what I mean by bi directional it means that if you had a scanner that was capable of communicating with the powertrain control module and turning on the low speed fan when you request it. So instead of waiting for the car to heat up and the coolant to get hot and wait for the fans to turn on, you can just plug in your scanner, go to the output mode of the powertrain control module and hit a button, and it'll turn on low speed for you. And what this will do is it will give you a quicker way of getting through your diagnostic process. And then you can also have the scan tool click on high speed, which would then turn the high speed fans on, and you can get a sense of what's working and what's not working on the car and make a quicker diagnosis and The same thing applies to the trump release circuit that we talked about earlier in this course. If you have a scanner that has the capability of turning on and off devices that the body control module controls and also monitoring that the data that the body control module receives it can help with your diagnosis. For example, when we were doing the trunk release, we were relying on pressing a switch and trying to eliminate things as best we could without having a scan tool. But if you had a scan tool, you could actually without having to make a test using a volt meter to find out if the voltage is there, I could actually go into the body control module data press, the Drunk Release switch, and the data would show me Drunk Release request or trunk release idol or something like that where it's telling you if this circuit is working just by looking at it on a scandal now we could do the same thing. Like I show you in the prior video of putting a volt meter at Pin nine or a Terminal A. And if I see 12 volts, that means the switches and pressed. And if I see zero volts, that means this, which is pressed. So what the scanner does is it definitely shortcuts it, especially if the circuits working. Because you could just look at the data on the scanner. It might say Switch Idol. And then when you press the trunk release, which it will say Trump released request or something like that, and that would then eliminate this whole circuit from your diagnosis. And additionally, you could also in the output control section of the BCM. If you have one of the bi directional scanners, you could tell it to command the trunk to open, which would, in essence, just close this switch for you inside the body control module at your request, so that you could then listen for the click or diagnosis the rest of the circuit. So the scan tools definitely have an advantage over not having one. But like I showed you earlier in this course, you can work around with a few additional tests or by unit diagnostic thought process. You can eliminate most of the picture anyway. It may take a little bit more time than if you had a scanner, but it can be done either way now getting back to the cooling fan circuit. The other thing when we were talking about diagnosing the cooling fan and running the car and waiting for the coolant to heat up to the first threshold, which would turn the fan on and then the second threshold, which would turn on the high speed. The scandals would also have a way of monitoring the coolant temperature as it's increasing in value. So you could see if the sensors actually working and reaching the value up to where it should turn on the switch and then see if the fan then comes on at that temperature. So if I look at this picture here, what you would be doing is you would actually be getting with the scanner. You would be getting the information inside of the engine control module, where it's reading the temperature from this coolant temperature sensor, and the way they do it is by creating a series circuit using a resistor that's inside the engine control module in Siris with the coolant temperature sensor, which is a device called Arthur Mr. And if there Mr changes its resistance based on temperature at the end of the course. In the next Steps video, I will give you some links to some additional sites that can provide additional information about the misters and some of the other things. We're talking about us as as well as a couple of recommended links on how to use a multi meter and using it for diagnosing certain automotive circuits on your car. I'll provide those links for you in the next steps video at the end of the course. But what the scandal would do is monitor the temperature of the engine by knowing what the voltage would be based on the different cooling temperatures that are possible. So as the engine heats up, the voltage that's across the resistor inside the module is going to change because the resistance of this ther Mr is changing and that change in voltage is going to actually coincide with the temperature of the coolant in your engine. Now in the future, I may create an advanced course and give you more detail about Holmes law, how it relates to voltage current and resistance and give you a way of understanding the inner workings of how some of these sensors work, but for now, just realised that the engine control module has a way of knowing what the temperature of your colon is by monitoring this author Mr Circuit. And if you have a scan tool, you could see the reading of the temperature of the coolant right there on your scanner if you wanted to tell if the engine control module was turning on the fans at the right time. Scanners condemn finitely Be a big asset to your diagnosis if you're going to be doing this for a living, and if you're going to work on your car, perhaps some friends cars and you're seriously going to try and save some money with this, it might be worth spending a few $1000 on something that's a quality product that could do bi directional control for you and also read some of the data from some of the modules. But for most people that are do it yourselfers, this may not be practical, and it may not be worth the expense. So that's something that you'll have to decide for yourself. But just know that those things are available, but the choices are There are so many in the next video. We're going to continue diagnosing the cooling fans circuit, but we're going to do it in a different way that will enhance your understanding. It's a way that I call reverse diagnosis. 27. Video 26 Cooling Fan Fault All Fans Inop: in this lesson. We have a condition where none of the fans were so low. Speed doesn't work and high speed doesn't work. And the problem here is on the surface. You would think, Well, how can I eliminate anything if there's no part of the circuits that worked in the other faults, We had the low speed or the high speed working so we could eliminate parts of the circuit because the low speed was working in the one example and because the high speed was working and the other example. But now we have no part of the circuit working. So what can we do? And the answer is to deduce what could be wrong and where the fault would have to be to cause all of the fans to not work. It's kind of like reverse engineering. So I brought up the pictures of low speed in high speed, and what we're gonna do on the right is just highlight the parts that it can't be and see if we can leave ourselves with what could be wrong. That would allow no fans toe work, and we're looking for one fault that would cause all of the fans not to work. So let's start with the first power load and ground circuit. If there was a fault in this part of the circuit, the wire going to the relay switch and this wire going down to the coil down toe, low speed, let's say that that whole circuit was dead, either because of an open here or because of an open in this relay or an open in this wire or even a blown fuse. Would that cause all of the fans not toe work? Or would I have some of them working because the other fuse is still good and the arrest of the circuit has power load and ground available? And the answer is a fault in this circuit would not cause all of the fans not to work. All it would cause was low speed, not to work. And for the right side, Fan would not be able to work in high speed, But I would still have the high speed switch for the PCM would still be able to turn on these two relays, and with this relay on this fan right here, the left side fan would turn on in high speed so we would have one of the fans spinning on high speed. We might have a condition where the temperature gauge goes up a little bit high before it turns on the fan compared to what the customer is used to. But it would cool the car off, and in most cases you might not even have a fault where they bring the car in, other than perhaps either the temp gauge going up too high or the fans making a little bit too much noise. So because that can't be the fault, What we're gonna do is we're gonna highlight that in as eliminated, and the same thing goes with the rest of the low speed circuit here. If there was a fault anywhere between here and here all the way up to this point and even all the way through the fan over here, it would not cause none of the fans toe work. Now, there is an exception on this one wire right here. If we look at this wire, is this wire needed by the high speed circuit and the low speed circuit? And if I look at my pictures, it is the ground for this fan and this fan when it's in high speed, and it is the ground for both fans when it's in low speed. One of the possibilities is this wire between S 1 48 and G 101 That could be the fault. So that's one of the things that we would have to check to find out why these fans are not working at all. But we can eliminate this fan itself and this wiring all the way back through here. So let's highlight that as well. And even up in here. And why can we eliminate this fan? Because if this fan let's say this fan was open and open, even if it was missing, the connector was off of it. Would I still have? If this was the only fault? Would I still have the right side fan with a path through here? This relay would be on here with their be a path through here to ground, and the answer is yes. So the right side fan in this case would be on high. Neither fan would work on low because the fans Aaron Siris on Low and the open in the left cooling fan would prevent there from being a complete path to ground for low speed. But for high speed, we would have the right side fan working. So again we can eliminate all of that part of the circuit and we can move on. And we know that one of the areas now is going to be this ground wire that could cause none of the fans to work. So let's continue on. What about if this high speed switch did not work this wire here and this path through the relays all the way up to power? What if this wire from the fuse all the way down two high speed cooling fan If there was a fault in one of those areas, if it was here, would we still have low speed operation? And if you look at your low speed picture, low speed doesn't need that wire. It doesn't need the relay coil. It doesn't need this relay coil. It doesn't need this relay switch. So if there was a fault in any of this wiring on the low speed circuit, that's not highlighted, then low speed would still work. However, look up at the very top here, look at this little section, all right? And this is this section right up here. If there was a fault in that little section right up there, would that effect both low speed and high speed. And now let's look over at our highlighted pictures again on low speed. I need that little section of wire as well as this section of ground and on high speed. I need that little section of wire for any of the circuit to work. And I also need this ground down here for any of the circuit toe work. In this case, we have a situation where we know that the fault has to be either in this wire right up here from hot at all times, up until this junction point or from this junction, point down to the ground. And we can eliminate that with one test at the fuse box. If I come up over here and just measure for 12 volts at this location, if I get 12 volts than I know, it's not this wire. And I know my fault is in the ground path and then I can just go check at the ground. And while it's true, you'll know that the fault is in this ground. You would then have to understand how toe find that on the car, which is another lesson in itself. You would have to have access to the locations of where these grounds are, and you would have to understand how to take apart perhaps a harness or make a test on the car to see where the problem is. If I was doing this on the car, what you can do is create a power load and ground circuit using what's called a test light or a circuit tester. And here is a picture of what that tool would look like. Thes air all circuit testers where if you connect the alligator clip to negative battery and touch the probe tip to positive battery, it lights up the circuit and depending on which way you hook it up. If I hook this alligator clip up to ground, then I have load and ground, and I used the tip to find power. But if I wanted to find if a ground was good, I connect the clip to the positive side of the battery, and now I have in my test light or circuit tester. I have the power side and the load, and I use the tip toe Look for a good ground. And in the case of the example that we're doing right now, let me move this out of the way. I would want to hook it up to positive battery the alligator clip, and then I would want to touch a wire to test if it was ground. Now, once I've eliminated this power wire up here, I know that the fault is in the ground. So what I would do is I would actually remove this relay over here if I was working on this car. Because of this relay is much easier to get to than trying to disconnect the wire from the fan and probing it, or from trying to find this splice, which is usually taped in the harness. So since I know that this wire has to be good, because if this wire was bad, it wouldn't have been causing all of the fans toe, not work. If I was to remove this relay and connect the probe tip of my test light to Terminal B six and then connect the alligator clip to positive battery. What I have is power and load, and I'm trying to make a circuit using this ground. And then what I would do is I would find the location of where this place is, and I would find the location of where this ground is, and this requires a shop manual To do it. You would look up component locations, and you would try to find where that ISS And in many cases, if you have a factory manual, you will be able to find it, and in other cases it could be a little bit difficult. But often times you can just trace the wiring from the fan to where the ground might be now . In this course, because of copyright rules, I can't demonstrate doing this or going through this activity using the manuals from any one of the programs of software programs, because you need to own the rights to that in order to do that. So that is something where you could purchase a shop manual, access for your car or for a group of cars and pay a monthly fee through a company like all data, who makes shot manuals and then tries to sell them to the general public and to businesses . And then you would have a way of looking up for locations of these different components. But as Faras teaching you here, I can't demonstrate that live for you because of the copyrighted information. And even if I have access to look at it myself, I don't have access to make. It is part of a program that's for sale, getting back to what I would do once that the Eslite is hooked up from positive battery to Terminal B six. I would then go down to this area where the ground is located and where this place is located, and just move the harness back and forth a little bit and see if I could get the test light toe light. And as soon as I have a good ground, that light will light. So if I was to move this ground and just pull on the wire work, move the wire side to side and I was able to get the light to flicker, Then I would know that I'm right near the location of where the faulted and there are some cases where you might have to find this place and cut the wire here and spice in and find and location of where this ground is good. Maybe it's good up until a certain location, and you would have displaced in a new piece of wire to repair it. So as we look over this picture now, even though we did not have any information about what to eliminate because low speed didn't work and high speed didn't work by just using deductive reasoning and figuring out what could cause all of the fans not toe work just by figuring that out and spending a few minutes with schematic and because we understand it from having highlighted both pictures, we can much more easily determine where the fault has to be in the next video. We're going to spend a little time doing a little more of this deductive reasoning, and I'm going to use the same schematic because if you use a schematic, you know, then you can understand how beneficial this can be. And then when you try it on a different schematic, you're just gonna need to spend the time to analyze what does low speed look like or what does high speed look like. And if you get used to coloring in the power load and ground, then when you do your diagnosis, you will have the information you need to get quickly to an end result that you'll feel proud of. So I'll see you in the next video. 28. Video 27 Cooling Fan Faults Reverse Psychology Diagnostics: in this video, we're going to try and match the fault to the scenario of what the fans would be doing when they're commanded on low and commanded on high. And this exercise can go a long way in developing your understanding of schematic diagrams . It's almost like you're learning the schematic inside out. First, we're learning where I give you the condition and you try to find the fall. But in this activity, I'm giving you the fault and you're trying to find the condition. So if you come over here on this left side, I have five different scenarios of what the fans would be doing. The top one up here is what normal operation would be. So that means if the PCM commands low speed fans on both the right fan and the left fan should come on low speed. And if the PCM commands high speed on meaning in this case, high speed means I turn on the low speed switch. And then, after a three second delay, I turned on the high speed switch because that's how this circuit works In the description In the operation, a different car or a different model may work differently where only the high speeds which comes on, and maybe different manufacturers do it different as well. What we want to do is get to understand the picture well enough, so that regardless of what the picture looks like, a different variation will be able to decide what's going on. So normal would be low, low. Hi hi. And in one of the examples we had, where the low speed fan was not working, what we would have had their had we commanded low speed on, we would have had this second scenario off off when Lo was enacted. And we would have had high high when the high speed fans were commanded on and the same with low speed when low speed was working. But high speed was not. The results of turning on the fans on lower on high would have brought us this chart down here where we would have had low low and we would have had off off. What I want to do now is I want to give you a fault, and let's say the fault is that there's an open in this wire right here between the right side cooling fan and the fan control mode relate. And what I want you to do is tell me what scenario we would have when the fans are supposed to be on low and when they're supposed to be on high. What result would we get? So pause. The video is second and take a look and see if you can figure it out. Okay, So if there was an open in this wire and it wouldn't matter where it was along this wire anywhere along this wire here or even if the right side cooling fan was open and not working, it would all cause the same result. And even this wire right up here. So if there was an open here in this wire, the result would be that the low speed fans wouldn't work. Because if you look at your low speed highlighted picture, this wire is needed for low speed. And if there's an open in this wire, the whole series circuit will not work. We would have off off for the result of commanding the low speed fans on. But what would happen when we commanded high speed? So, in order to enact high speed, this switch closes which will bring this switch over. But because of the open here, the right side fan will not come on. So the right side fan is going to be off. But what about the left side fan? When this switch closes, it will turn on this relay and this relay, and this open over here is not gonna affect either of those. And then once this relay closes, it will allow the left side fan to operate on high speed. So what we would have is a scenario where we have off off, and then the right side fan would be off and the left side fan would be on. All right, So here's another scenario. What if we have a bad relay the fan control relate to and the switch doesn't close? And that could be because of the switch itself being bad or this short wire right over here being bad or this short wire over here, they would all cause the same thing. There would be an open circuit here, and it would even be the same fault or the same scenario if this relay was open or if there was a problem in this wire, up to this point. And if we had that kind of situation, what would be the results when we put the fans on low and then we put the fans on high? Do you look at your highlighted pictures again? If we were to command low speed fans on, we would expect to see both fans on low. And since the Open is either over here or over here, it doesn't affect the low speed operation. We have a path through this fan and through the other fan to ground, so low speed would be on and we would have low low where both low fans are working. And then what would happen when we commanded high. When we command high, we still have this relay energized, but we're also trying to energize these other two relays when we energize this one by closing this switch down here, this will definitely pull over and provide a path to ground for the right side fan, which would now be on high. But on this side here, the left side fan. If this relay was open, where this wire or this switch or this wire, the left side fan would not be able to operate on high. When we commanded high, we would have left side fan off and the right side fan on high. So let's do one more and this one's going to really challenge you. What if the fall was that the fan control mode relay? The Kewell was open so that it will not pull the switch over when the high speed cooling fan relate control is turned on. What would the result be when low speed is commanded and when high speed is commanded? See if you could fill in what the resulting scenario would be. This may take you a few minutes and you might have to think about this one a little, but see if you can come up with an answer. Okay, so we have a fault where there's an open in this relay. And if you look at your low speed picture, we know that an open in this relay in the coil side would not affect the low speed operation, because I would still have a complete path through the normally closed switch through the other fan in Siris to ground. So the answer for commanding low the result would be low and low because the right side fan and the left side fan would both come on in low speed. However, when I turn high speed on, I would then power up this relay which would pull this switch over, which would allow a path for 12 volts to get to Terminal A of this fan. And since B is connected to ground already, the left side fan would come on high speed. So for the left side fan, I could put high. But what about the right side fan? What would that do in this situation? I would have 12 volts right over here, a terminal, A of the right side fan. But would there be a ground pass if I went through this fan and came up here and went through the normally closed contacts? Remember, Now we want this relay switch to be pulled over so that it gets its own ground. But in this case, since this relay coil is open, we would still be going through the normally close contacts which would come up to this spice area. And how much voltage would be on this wire when fan control relay to is energized, there would be 12 volts there. So if I have 12 volts on this side of the fan, the same 12 volts would be available all the way over to here. So if I have 12 volts here and 12 volts there, there is no difference in potential across the fan. And the fan operates because one side has 12 and the other side has zero, and the fan wouldn't care if it was backwards. Either would just spin the other way, But in this case, we have 12 volts at Terminal A and 12 volts at Terminal B, and the right side cooling fan would not spin because there's no difference in potential. But the left side cooling fan would have 12 volts here, a terminal A. And since Terminal B is connected to ground, the left side would work on high. So in this case, we would have lo and low for the commanded low position and for commanded high. We would have the left side fan would be on high, but the right side fan would be off because there's no difference in potential. So the answer here would be low, low off, and I I hope you've learned a lot from this course and from the diagnostic procedures and techniques that I'm teaching in this course. If you apply these over and over again two different pictures and spend some time with the different pictures and highlight the on and the off the high and the low of whatever you're working on, you will be amazed at how quickly you will be able to analyze schematics as time goes by in the next video, we're just gonna tie up some loose ends and I'll give you a few websites that I think could help you with some additional information, perhaps about learning about your meter if you want to buy a meter and perhaps start learning about how to use that on the car, there some good videos out there that are free, and I want to point you to a few Resource is that will help you. So I'll see you in the next video and will wrap things up for this intermediate course. 29. Video 28 Before You Blame the Module and Next Steps: this video is titled Before you blame the module and next steps and in the first part of the video, I just want to give you a few tips on being careful about replacing different modules on the car when you think your diagnosis leads that way because modules will not operate their devices unless all of the conditions are met that required for it to operate it based on its programming, you might be able to con somebody into doing something that they don't want by pointing out that all this is like this and this is like this. So why aren't you turning this switch on in a case of a computer? If there are three things that have to be met before it will turn the switch on, all three of those things will have to be met or the computer will just sit there waiting for that tow happen, for example, you might come over to this circuit, and in your diagnosis you might give a ground to this wire here. And if you give a ground to this wire, it would turn on the low speed relay, which would turn on the low speed fan And if you were blaming the module now the powertrain control module for not turning on the low speed fan, you would have the expense of getting a new module and getting the module programmed, which nowadays needs to be done at a dealer or somewhere that can program modules. And you could be entirely wrong, because what if the coolant sensor circuit is having an issue where the proper temperature hasn't been reached yet? And maybe it's just a little bit off where it's taking too long to come on? Maybe there's resistance in the coolant temperature circuit. And what the reading on the gauge used to be for the customer or for yourself where it used to turn the fan on has now changed to a different reading. And if you're blaming the module for something, it's not doing it. Maybe just waiting for the right signal for it to then do its job. The same is the case in the trunk release circuit. The description and operation of the trunk release circuit says that when a request is made by pushing the trunk, really switch that the BCM will close this switch, giving power to the trunk relay, which will then pop the trump by activating the trunk release actuator. But the description and operation also says that the car needs to be in park or neutral before the module will do that. So if you came over here and gave power to Terminal C because the trunk release which was working when you tested that, and then you were thinking that the BCM is not doing its job by putting power here, and then when you applied power here by disconnecting this connector from the BCM and putting 12 volts there, you were able to get the Trump release actuator toe activate. That does not necessarily mean that the body control module is bad, because the body control module could just be following its programming, waiting for the car to be in park or neutral or, in the case of perhaps, a defective park neutral switch. The BCM thinks the cars in Dr because that's the signal it's getting. And it may never popped the trunk because to the BCM, the conditions that it needs to activate the trunk release have never been met, and you could go down the line with any of the modules on the car when they are controlling an output on a specific circuit. There are conditions and criteria that need to be met before they will actually activate. And some modules will have 123 or four or even mawr criteria before they will operate something where, in other cases, it may just be one piece of information that it needs. Maybe it just needs a switch input, and then it will pop the trunk. But in the case of this trunk release, it needs to switch input from the trunk release, and then it also needs the car to be in park or neutral. So make sure you read the description and operation before you go. Parts changing crazy with modules because you'll wind up disappointed and out quite a bit of money because they do cost some money and they cost money to program, and then the result you get will be less than satisfactory. The other thing I wanted to do in this video this last video is show you just a couple of pictures that illustrates some of the components we've been talking about. This is a picture of an under hood fuse box and on the covers. Oftentimes they'll put an outline of what the different components are inside the fuse box . So the picture on the right I have the two covers off, and we've been talking about the Cooling fans circuit. And if you look at the cover on the left, this lower one, it has the three different fan relays here, and when you take the cover off, you would have to three different fan relays and notice that two of the relays are the exact same type, which would coincide with our fan relay. Juan and Fan relate to, and this other style relay, the model 36 02 is a single pole double throw relay, which would be like the fan mode relay we've been talking about and one other thing to mention. While we're here in the picture, some manufacturers will use what's called Maxie size fuses to feed another group of smaller size fuses. The battery will supply power to the fuse box, and then they may have 1234 or several more Maxie fuses, and this maxi fuse may feed ah, whole bunch of circuits in this fuse box, or it may actually power up a bunch of fuses in a different fuse box that could get wired to another fuse box. And it does it so that you have a way of disconnecting power or protecting power to certain circuits by having like a tree system set up. So you have the main battery. You break it down into these maxi fuses, and then you break each maxie fuse down into a bunch of smaller fuses. And when I'm talking smaller, I'm talking smaller in average, and in this case they're smaller in physical size. But one place you have to be careful is that the rating of the fuse is what matters, not it's physical size. If we were to look at these three fuses that I have shown here, the one on the left is a maxi fuse, which would normally be used to feed a bunch of other circuits. The 30 on here means 30 amps is what it will protect for meeting. The fuse will open if more than 30 amps goes through it. Notice how these other two fuses they're different sizes. This is a mini fuse and a regular sized fuse. If any of these three had more than 30 amps go through, they would all blow. The larger physical size would not make a difference at all. This view's could protect the same circuit that this views can. But many manufacturers will use a larger size fuse called a maxi fuse in part of its tree structure, where then they'll have a bunch of other fuses being powered up by this maxi fuse that are of lower amperage. If it's a 30 Aunt Maxine views, chances are it's gonna be feeding fuses that are five and 10 AM, where maybe 15 amp in its structure. But if I'm using this mini fuse as a 30 the maxi fuse that's gonna be above this one and the tree structure of fuses the way they design it would probably be one of the 60 and fuses. And then underneath that in the power distribution, you would then have maybe a few different 30 amp or 20 a M or 15 and fuses that are fed from that 60 and Maxie fuse. The point here is to remember that the physical size of the fuse has nothing to do with if it blows quicker or not. All three of these fuses have the same exact rating. The last thing I want to show you is a couple examples of some of the relays that might be used on different cars. Many relays, or most of them, will have a drawing illustration of what the different terminals are on the relay and what the schematic of the relay looks like. Here we have the relay coil and terminals 85 86 go to the relay coil, and here was showing that the switch site of the relay uses terminals 30 and 87 30 is actually connected to the side. That's the pivot, and 87 actually gets connected to the site when the really activates and the switch pulls over. And then, if I was to pull this relay and turn it so that you can see the bottom, you could see that they label the four terminals here on the relay with the number here, so this terminal would be 30. This would be 87. So you do have to be careful if you're trying to find these terminals on the car, because when they draw the picture of the relay, notice how 30 and 87 are right on top of each other. But on the electrical contacts of the relay itself, notice how they're diagonally across and the same with E 85 86. These two terminals are actually going to the coil, and they are 85 86th. But in reality, there, at a diagonal and on the picture, they draw them straight up and down because it's just easier to understand the picture that way by having it not cross diagonally. And he was just another example of a different style relay. Whether terminals may look different, but the numbers and contacts are the same. In this case, this one's a single pole double throw and one other thing to note. It is common for some relays to use these terminals 30 and 87 87 a 85 and 86. But there are other manufacturers of relays that may use a B, C, D E E or 12345 And it doesn't matter. As long as they give you a picture of which number coincides with which part of the relay, you should be able to then lift it up and look at those numbers and make some type of test on the terminal that you need to. So let me take a minute to say thank you for purchasing this course, and I hope you've gotten an enormous amount of information out of it. If you practice what is taught in this course on different schematics, your skill level will improve greatly. And the amount of time that you spend trying to diagnose or figure out what's wrong from a schematic will get cut in half and then cut in half again toe where it's taking you very little time to figure things out. If you check out. The additional resource is for this lesson. I'm going to put a PdF file that has some links to some free sites where you can see some on car demonstrations and also some information about how to use multi meters for people who want to start to do some of the work themselves. So the links that I provide are some that I've found to be of decent quality and they're worth looking into so you can get further information about automotive diagnostic. Some of that will not be on Lee Electrical. Some of these sites have information on other areas of your car, but feel free to snoop around on these sites and see if you find something of interest to you. And if you want to drop me an email with an idea for another course. I've already had some ideas about starting and charging system that people have asked about and windows and door locks, and I may try to make some courses in those areas. It does take some time to make him, so it will take a while as long as there's a need for it and people are buying the courses and they're received well, I will continue to keep making some, and if you give me an idea for what you'd like to see, I will do my best to look into it and see if it's something that I could provide value for . So have a great day and thanks again for purchasing this course