I know this type of video takes a lot longer to make, but these test your showing is what it takes to find the problem, and what people don't realize goes into being a professional, and not guessing. Greatly appreciate your channel
I've learned a valueable lesson on a Lexus recently. Always disconnect the battery before plugging or unplugging any modules. The lexus has a psc module that is bolted to a bracket. The module grounds through that bracket. I unbolted the bracket doing some other work. I had turned the ignition on checking some voltages in the fuse box and bumped the pscm which allowed the bracket to contact the chassis that it is normally mounted to. After fixing the original issue the vehicle ended up having multiple comm codes along with 4 of the 40 modules off the network. Ended up finding out the pscm was dragging that leg of the network down. The module was damaged which cost a lot of coconuts. I'm just thankful none of the other modules were damaged. Been doing this for 28 years without damaging modules, but that day changed my processes.
It is very hard to find a good diagnostic anywhere, especially on RUclips. You are a professional. You not only fix problems but you also try to show and teach us how to do it, speaking slowly and clearly so that we can understand. I really appreciate your time and the effort that you put into it. Keep up the good work! I wish you all the best!
Well I have to disagree with you Jake. If you think you’re an idiot for forgetting one thing I think all of us are doomed. Your knowledge is so impressive to me. I know it’s a figure of speech and we’re our worst critics. Keep up keeping up. 👍
Love that you show the different techniques and why one may be better than the other. Videos that show testing techniques and why one may be better than another, may help some from going down a rabbit hole. Great job!
Hey Jake the 3.6 has known issues with the oil pressure sensor pigtail deteriorating and the 5V /Grd touch pulling the circuit down causing multiple codes including some of the codes you have. This pigtail/ sensor is under the intake manifold on the oil cooler. Try to borescope the pigtail under the rear of the intake manifold.
Like the video showed, you have to completely isolate the circuit from any power source to check resistance. The Fluke 87 is very good DMM, unfortunately it is not a low resistance meter. Another way to say this is the Fluke 87 is effective at low ohm continuity but not sub Ohm resistance (mOhm, uOhm) measurement. In its simplest form an Ohm Meter supplies a known test current into the circuit and then measures the voltage across the circuit and then converts to DC Ohms by Ohm's law. The Ohm Meter is apart of the circuit so if there are any voltage sources within the measurement it will modify the reading. With any Ohm Meter we have to understand what resistances it was designed to measure. Automotive load testing is primarily used to find faults in wiring conductors and connections. Loads can also be used to test module power outputs if you have a load that is a good match for the output. However, once you have established that the wiring and connectors are good then in diagnostics the fault is usually attributed to I/O, either form a module or switch etc., which is usually looked at with the first test done either with a scope (for dynamic I/O) or a DMM (for static I/O). After testing the wire and connections you can go back and measure the I/O again to confirm, but this is usually only done to capture a final scope trace to provide to the customer. In practice the failure modes found in vehicles due to corrosion in wiring and pin connections, bad relay output contacts or low pin tension will result in a very high circuit resistance which will be easily detected using a load current of 1 Amp, which is the smallest ATO size fuse (which will supply 1 Amp indefinitely, see time-current curves from LittleFuse). We want to load test without overloading the supply fuse, so you are relatively safe if you don't use a load over 1 Amp as a starting point.
Excellent, very well explained diagnostic procedure, Jake! When using an ohmmeter it's important to remember that the meter applies a small DC voltage to the leads, to measure the resistance (voltage level depends on the meter range used) and, if there is a spurious voltage on the circuit, it will bias the meter reading! An easy check is to reverse the leads - if reading changes, there is a spurious voltage on the circuit. Wondering if something else could drop the PCM voltage, other than the PCM itself and the only possibility I could think of, is some sort of corrosion inside the plug, pulling the 5V pin to a nearby grounded pin, but only when all pins are connected to the PCM.
Excellent video Jake! If I don't have a reference voltage supply by PCM and like in this case is not being cause by the sensor or another sensor circuit and I am calling the PCM as the root cause of the problem I have to make sure all voltages supply to the PCM are reaching the PCM as well as the grounds. There are some components that needs those grounds! Powers and grounds check before advising a new ECU. Also, I would have tested the other sensors reference voltages the same way you did with this circuit to have a better picture for analysis.
The reistance gets thrown off because the multimeter does not directly measure resistance. In resistance measurement mode, the meter actually applies a known voltage to the circuit and measures the current through the circuit, then uses Ohm's law to determine resistance and the result is displayed as ohms on the meter. R=V/I. Add stray voltage or current from another source and it messes up the measurement because the meter has no way of knowing that the stray voltage or current is coming from some place other than the meter.
Thanks for sharing Jake . Wow I never heard someone say that as a troubleshooting strategy . I’ll be thinking of that probably till you post part 2 . Thanks again 👍
Great case study Jake. 😎👍 BTW... I scan that QR code with my phone to send to my customers the Pre and/or Post scans via text or whatever method they may want. I find it to be really handy. Looking forward to part 2.. Cheers
Many sensors ground internally in the PCM (Sensor Ground) so if you unplug the PCM your also removing the sensor ground, if a sensor's 5v is shorted internally to sensor ground unplugging the PCM would make the short go away when just checking between 5v supply and chassis ground. I would want to check for shorts between the 5v supply wires and the sensor ground wires as well before condemning the PCM.
Hi Jake, The ultrdiag should be able to screen record. Actually, I really love this scan tool for this feature. Which the graphing could be better, though. Thanks for the video and the explanation with using resistance as a test.
i swear you must be watching me at work 🤣🤣🤣🤣 i almost got caught out earlier this week with that ohm check on an ecm circuit i was testing but something in my gut was telling me “that ain’t right “ and oh yes voltage on the line 🤪🤪🤪 i tell you i have hunted that test light and over here it’s as rare as unicorn 💩
I noticed a long time ago that I would get false ohm readings using my Fluke 77 and couldn't figure out why (scratch head). I did discover that my Simpson 260 an old school analog meter (with a real meter LOL) would read correctly! I suppose the Simpson's meter would 'load' the circuit somewhat and give a more acurate reading. I really don't know.
Need to test Voltage and ground on the pcm, one more question if any of the other sensors share a 5v reference, maybe one of them is short circuited and of course the 60 ohm pcm resistance at the end 😊😊😮
Computer Powers and Grounds. Is the PCM Internal APP Ground Ref above or at PCM Ground? What other PCM inputs/outputs can cause the 5 Volt References to be at zero volts. Plug in APP connector at the back of the engine and measure APP 1&2 5 Volt Powers and Ground References shorted to chassis Ground by testing at the disconnected PCM connector pins. Verify those connections and/or the APP assembly or wiring through the bulkhead are not shorted. What about the APP assembly itself? It's a start.
Jake I just watched the video again and if you replace the PCM now is it a new or used PCM ? Are there any other sensors using 5v you could disconnect to bring the 5v ref. Back to life ? I’m just running this thru my old brain . Everyone usually says check the PCM for a good ground . To be honest let’s hope that the new PCM just fixes the problem . I’m trying but I’m just a retired old Aircraft Mechanic trying to learn these electronic time machines. Lol. 😡Artie
I'm wondering, when you had your testlight connected and it was lit showing a short to ground, couldn't you just unplug the module connectors and if the light went out it would indicate the short is going through the module and or the module itself is shorted. So now if the short is going through the module could it be connected to another external sensor that may be shorted pulling the 5 volt ref circuit down, the old voltage follows the path of least resistance rule. So if you find that sensor and unplug it, your short will go away and your 5 volt ref will return? Is it possible that the circuit could be shorted to ground by a sensor that shares the 5 volt ref? This is my thought. Can't wait for part 2.
In sensors that are variable resistance they are called either pull up or pull down circuits. So the bias voltage is there for the sensor to pull down to the what ever the sensor is calibrated to operate at.
@autodiagyt My friend, the 5V line is shared with the crankshaft sensor and the oil pressure sensor. There may be an internal short circuit in one of the sensors, or a short circuit to ground with the crankshaft sensor or ground with the oil pressure sensor.
Hi, I have one question and if somehow maybe you can help :) I' am from Europe(Serbia) I have Opel Astra K 2017, a few mouths a go I have problem with my power steering weel , so I bought a used from some creased car but is very good condition, we puted on my car and it's working, but tracking assisten line not, so I plan to by VXDiag Nano for GM and try to reprogram this part, Is this possible?? Or Can you help me with this??? Thanks you for your advice and answer
It’s possible but might require special software. Sadly I don’t think I could help because I’m on the North American servers and you would need someone with European server access.
The issue with an LED Test like is that it's almost no current and the circuit of the LED is very voltage dependent, it's either enough voltage to turn it on or not. It's hard to get a LED to just be dim. I think most LED Test lights only load the circuit to about 15milliamp so my test light pulls about 4 times that and is still computer safe. I'm not even sure a LED Test light will turn on with a 5v circuit but my test light does, which you will see tomorrow in part 2.
Correct but sometimes it’s hard to tell that the circuit is live. Like in this case the ignition was off and you could no longer communicate with the scan tool so you would logically think the module is asleep but it’s still powered and trying to do things.
I know this type of video takes a lot longer to make, but these test your showing is what it takes to find the problem, and what people don't realize goes into being a professional, and not guessing. Greatly appreciate your channel
I've learned a valueable lesson on a Lexus recently. Always disconnect the battery before plugging or unplugging any modules. The lexus has a psc module that is bolted to a bracket. The module grounds through that bracket. I unbolted the bracket doing some other work. I had turned the ignition on checking some voltages in the fuse box and bumped the pscm which allowed the bracket to contact the chassis that it is normally mounted to. After fixing the original issue the vehicle ended up having multiple comm codes along with 4 of the 40 modules off the network. Ended up finding out the pscm was dragging that leg of the network down. The module was damaged which cost a lot of coconuts. I'm just thankful none of the other modules were damaged. Been doing this for 28 years without damaging modules, but that day changed my processes.
It is very hard to find a good diagnostic anywhere, especially on RUclips. You are a professional. You not only fix problems but you also try to show and teach us how to do it, speaking slowly and clearly so that we can understand. I really appreciate your time and the effort that you put into it. Keep up the good work! I wish you all the best!
Got the popcorn out...Is it going to be a bad PCM? PLACE YOUR BETS NOW! ;)
Well I have to disagree with you Jake. If you think you’re an idiot for forgetting one thing I think all of us are doomed.
Your knowledge is so impressive to me. I know it’s a figure of speech and we’re our worst critics. Keep up keeping up. 👍
Love how you teach on your videos. I know im not the only one who learns from this. Thank you.
Love that you show the different techniques and why one may be better than the other. Videos that show testing techniques and why one may be better than another, may help some from going down a rabbit hole. Great job!
Good lesson and case study Jake! Thanks for posting. Can't wait for P2!
Hey Jake the 3.6 has known issues with the oil pressure sensor pigtail deteriorating and the 5V /Grd touch pulling the circuit down causing multiple codes including some of the codes you have. This pigtail/ sensor is under the intake manifold on the oil cooler. Try to borescope the pigtail under the rear of the intake manifold.
But didn't ohm testing the 4 5v circuits to ground show no continuity to ground, or maybe he should have lied tested the 4 5v circuits
It could be. 5v (camshaft 1 and 2, crankshaft, oil pressure sensor, tps, app, map sensor ) may be one of them shorted pull 5v to ground
Good call... i have watched part 2
Like the video showed, you have to completely isolate the circuit from any power source to check resistance. The Fluke 87 is very good DMM, unfortunately it is not a low resistance meter. Another way to say this is the Fluke 87 is effective at low ohm continuity but not sub Ohm resistance (mOhm, uOhm) measurement. In its simplest form an Ohm Meter supplies a known test current into the circuit and then measures the voltage across the circuit and then converts to DC Ohms by Ohm's law. The Ohm Meter is apart of the circuit so if there are any voltage sources within the measurement it will modify the reading. With any Ohm Meter we have to understand what resistances it was designed to measure.
Automotive load testing is primarily used to find faults in wiring conductors and connections. Loads can also be used to test module power outputs if you have a load that is a good match for the output. However, once you have established that the wiring and connectors are good then in diagnostics the fault is usually attributed to I/O, either form a module or switch etc., which is usually looked at with the first test done either with a scope (for dynamic I/O) or a DMM (for static I/O). After testing the wire and connections you can go back and measure the I/O again to confirm, but this is usually only done to capture a final scope trace to provide to the customer.
In practice the failure modes found in vehicles due to corrosion in wiring and pin connections, bad relay output contacts or low pin tension will result in a very high circuit resistance which will be easily detected using a load current of 1 Amp, which is the smallest ATO size fuse (which will supply 1 Amp indefinitely, see time-current curves from LittleFuse). We want to load test without overloading the supply fuse, so you are relatively safe if you don't use a load over 1 Amp as a starting point.
Thanks for the video and details. Audio was good in the garage.
Can't wait for the conclusion!
Great job I love your logic for diagnostic
Excellent, very well explained diagnostic procedure, Jake! When using an ohmmeter it's important to remember that the meter applies a small DC voltage to the leads, to measure the resistance (voltage level depends on the meter range used) and, if there is a spurious voltage on the circuit, it will bias the meter reading! An easy check is to reverse the leads - if reading changes, there is a spurious voltage on the circuit. Wondering if something else could drop the PCM voltage, other than the PCM itself and the only possibility I could think of, is some sort of corrosion inside the plug, pulling the 5V pin to a nearby grounded pin, but only when all pins are connected to the PCM.
Again great video, can't wait for the conclusion!
Excellent video Jake! If I don't have a reference voltage supply by PCM and like in this case is not being cause by the sensor or another sensor circuit and I am calling the PCM as the root cause of the problem I have to make sure all voltages supply to the PCM are reaching the PCM as well as the grounds. There are some components that needs those grounds! Powers and grounds check before advising a new ECU. Also, I would have tested the other sensors reference voltages the same way you did with this circuit to have a better picture for analysis.
The reistance gets thrown off because the multimeter does not directly measure resistance. In resistance measurement mode, the meter actually applies a known voltage to the circuit and measures the current through the circuit, then uses Ohm's law to determine resistance and the result is displayed as ohms on the meter. R=V/I. Add stray voltage or current from another source and it messes up the measurement because the meter has no way of knowing that the stray voltage or current is coming from some place other than the meter.
Thanks for sharing Jake . Wow I never heard someone say that as a troubleshooting strategy . I’ll be thinking of that probably till you post part 2 . Thanks again 👍
Great case study Jake. 😎👍
BTW... I scan that QR code with my phone to send to my customers the Pre and/or Post scans via text or whatever method they may want. I find it to be really handy.
Looking forward to part 2..
Cheers
great video Jake and good explanation of what was going on with the ohm meter. as usual I always learn something from your videos.
Funny to see that you also have an XFR laptop. I love mine.
I hate the touchpad on it but other then that I like it.
@ I just bought a Toughbook as a second system (might use it as my main programming computer but we will see).
Many sensors ground internally in the PCM (Sensor Ground) so if you unplug the PCM your also removing the sensor ground, if a sensor's 5v is shorted internally to sensor ground unplugging the PCM would make the short go away when just checking between 5v supply and chassis ground.
I would want to check for shorts between the 5v supply wires and the sensor ground wires as well before condemning the PCM.
Very good logical thinking, part 2 is out now so let’s see if your logic works out.
Hi Jake, The ultrdiag should be able to screen record. Actually, I really love this scan tool for this feature. Which the graphing could be better, though. Thanks for the video and the explanation with using resistance as a test.
I’m sure it will screen record I just haven’t tried lol
i swear you must be watching me at work 🤣🤣🤣🤣 i almost got caught out earlier this week with that ohm check on an ecm circuit i was testing but something in my gut was telling me “that ain’t right “ and oh yes voltage on the line 🤪🤪🤪 i tell you i have hunted that test light and over here it’s as rare as unicorn 💩
These are the test that trip techs up! It’s happened to me before.
Shoot me an email and I’ll see if I can get you one. GM changing the special tools website I’m not sure if it’s available right now or not.
great video thanks for such a simple and to the point explation
I noticed a long time ago that I would get false ohm readings using my Fluke 77 and couldn't figure out why (scratch head). I did discover that my Simpson 260 an old school analog meter (with a real meter LOL) would read correctly! I suppose the Simpson's meter would 'load' the circuit somewhat and give a more acurate reading. I really don't know.
Maybe load test the 4) 5v circuits from the disconnected computer side with the low current testers hooked to positive
Gold
Need to test Voltage and ground on the pcm, one more question if any of the other sensors share a 5v reference, maybe one of them is short circuited and of course the 60 ohm pcm resistance at the end 😊😊😮
If u have a 5v ref 2 circuit.. u could de pin 5v #1 circuit and jump to 5v #2 circuit..
Couldn't you just check for continuity between the PCM connector 5v to the TPS 5v wire in order to make sure you have the right wire?
Excellent video great stuff 👊🏻
Check powers and grounds at module before replacing module
Computer Powers and Grounds. Is the PCM Internal APP Ground Ref above or at PCM Ground? What other PCM inputs/outputs can cause the 5 Volt References to be at zero volts.
Plug in APP connector at the back of the engine and measure APP 1&2 5 Volt Powers and Ground References shorted to chassis Ground by testing at the disconnected PCM connector pins.
Verify those connections and/or the APP assembly or wiring through the bulkhead are not shorted.
What about the APP assembly itself?
It's a start.
Grasias
Thanks, professor.
Jake I just watched the video again and if you replace the PCM now is it a new or used PCM ? Are there any other sensors using 5v you could disconnect to bring the 5v ref. Back to life ? I’m just running this thru my old brain . Everyone usually says check the PCM for a good ground . To be honest let’s hope that the new PCM just fixes the problem . I’m trying but I’m just a retired old Aircraft Mechanic trying to learn these electronic time machines. Lol. 😡Artie
So did you disconnect the battery??
Nope. The difference was the PCM still awake trying to supply power to the 5v circuit.
I'm wondering, when you had your testlight connected and it was lit showing a short to ground, couldn't you just unplug the module connectors and if the light went out it would indicate the short is going through the module and or the module itself is shorted.
So now if the short is going through the module could it be connected to another external sensor that may be shorted pulling the 5 volt ref circuit down, the old voltage follows the path of least resistance rule. So if you find that sensor and unplug it, your short will go away and your 5 volt ref will return? Is it possible that the circuit could be shorted to ground by a sensor that shares the 5 volt ref? This is my thought.
Can't wait for part 2.
Very good logical thinking!
What is bias voltage? Is it used by the PCM for something?
In sensors that are variable resistance they are called either pull up or pull down circuits. So the bias voltage is there for the sensor to pull down to the what ever the sensor is calibrated to operate at.
Check the throttle itself if it's going to ground.
The red lead is not connected to Chassis. It is connected to the plug. This is floating ground.
The red lead shouldn’t be seeing ground at all.
Shouldn’t BOTH ends of the circuit be disconnected (TPS and ECM) to measure a short to ground on that circuit ??..should see OL if no short to ground.
I did that test later in the video.
@autodiagyt
My friend, the 5V line is shared with the crankshaft sensor and the oil pressure sensor. There may be an internal short circuit in one of the sensors, or a short circuit to ground with the crankshaft sensor or ground with the oil pressure sensor.
Hi, I have one question and if somehow maybe you can help :) I' am from Europe(Serbia) I have Opel Astra K 2017, a few mouths a go I have problem with my power steering weel , so I bought a used from some creased car but is very good condition, we puted on my car and it's working, but tracking assisten line not, so I plan to by VXDiag Nano for GM and try to reprogram this part, Is this possible?? Or Can you help me with this??? Thanks you for your advice and answer
It’s possible but might require special software. Sadly I don’t think I could help because I’m on the North American servers and you would need someone with European server access.
Can we you Led test light is that computer safe
The issue with an LED Test like is that it's almost no current and the circuit of the LED is very voltage dependent, it's either enough voltage to turn it on or not. It's hard to get a LED to just be dim. I think most LED Test lights only load the circuit to about 15milliamp so my test light pulls about 4 times that and is still computer safe. I'm not even sure a LED Test light will turn on with a 5v circuit but my test light does, which you will see tomorrow in part 2.
@ thank you sir for your service
❤❤❤❤❤❤❤
👍💙
12 min in, didn't notice any audio issue.
Yeah the echo isn’t hardly noticeable on the recording. In person it was much louder.
You shouldn't measure ohms on a live circuit at all
Correct but sometimes it’s hard to tell that the circuit is live. Like in this case the ignition was off and you could no longer communicate with the scan tool so you would logically think the module is asleep but it’s still powered and trying to do things.
You arent an idiot we all stumble on absentmindedness
Damn! You are goooodd!
You gotta watch part 2 and see what’s wrong with it!
@@autodiagyt
Already have!😀
FC keeps ppl like you me is business. Yep I would say PCM. I cloned many of them.