Checking for Power and Ground at an ECM

[@steliosslkds]

after 8 hours on internet and you tube i finally found a really helpful video!!!!!Thank you so much Scott not just for the info but for being precise and clear as an excellent professor!!my best to you from Greece!!!!

[@pigeonsil240sx]

look up "voltage drop test" its simple and mastering this is key to diagnosing power/grounds.

[@AlexanderMasara-q9s]

A very good video and demonstrate which side has voltage drop on circuit. Thanks very much

[@snapcookieftw]

This has been so helpful. It's been pretty hard as an electronic newbie to understand what voltage drop is and how it affects circuits. I now have some hope that my problem is not my ecm. Thank you!

[@brucetiller2360]

This explains alot as I'm now up to speed, awesome.

[@patbaptiste9510]

This video absolutely helped. I'm not an auto tech. but I am an electronic technician turned marine electrician who's currently looking to get auto electrical diagnostic and ECM troubleshooting and repair. I think my 24 years in the electrical / electronic field can be transferred over to automotive - that I'm confident about. so yes, I found this video to be extremely informative - especially the part which explains that most voltage drops occur on the *ground* side, due to corrosion. Of course I also understand that it can happen on the power / positive side as well but in any case, these tests are extremely important, so than you for sharing.

[@pantelis241]

Nice one, classic voltage drop test. Thanks 🙏

[@FarAboveDaCloudz]

Even the best mechanics shy away from electrical diagnostics. I commend your explanation of this often overlooked step in diagnosing faulty electrical components within a vehicle. Great job!

[@g00dl00kinb0i]

Ugh, I'm trying to avoid doing it but my Camaro throws knock sensor and o2 codes all day and it drives me nuts ! I checked most grounds on it except the hidden ones on back of heads and everything checks out yet I still get codes after just 1.5 miles driven... Now I'm gonna chase down the PCM wires and try some 100k Ohm resistors to test everything yet AGAIN. Thank you for the clear video !

[@michaelmowatt1951]

Thank You For Posting This. It has been very useful so far on my 2001 audi A4...now if I can just find that crusty ground on the ground side of the ECM @ 8.82 v ;0)

[@feeneysmechanical6215]

Awesome video Scott. Enjoyed the video

[@grtntgod]

Marvelous clarity, l have an open voltage circuit,l suspect the ECM thanks

[@AlexAutoFun]

Great video! thank you Scott!

[@francisdsa6790]

Very good explanation and demonstration thanks 💐👍👌🙏

[@ndigs]

You're the voice on my Udemy course!!!

[@rahrah8076]

Thank you!! That helped me a lot.

[@henrietta70]

Thank you for the best explanation. Im trying to find ways to exlude all other faults than ECM, to fault code on lambda heater circuit. Lambda is changed and there was nothing wrong with the old one. The car is petrol T4 Caravelle with AVT engine from 2001. Lambda heater gets both power and earth, from ECM. ECM earth is connected streight to battery terminal. I know the fault is in ground side, from ECM to lambda heater. The voltage dropps below 10.5V and the fault code is sett. If I measure voltage from plus wire and battery negative - the voltage is higher than from the pins between ECM and lambda connector. Testing closed circuit voltage test on ECM ground pins (they are two) gives me 25 mV. But when I test same test on the ground connection to lambda heater I get 7 Volts. The strange thing was, doing the same test on ground wire to after cat lambda, I got 13.85 Volts! But there is only a fault code on first lambda - not on the second one! Im I correct to presume its something inside the ECM, that is faulty? Early tests on ground taken from battery versus ECM: kzbin.info/www/bejne/hWXMZHWMf5t-obM Versus: kzbin.info/www/bejne/hXe5mniId9itq6M

[@ScottHadzik]

It sounds like an issue with the ground. Do you have a wiring diagram?

[@henrietta70]

@@ScottHadzik Yes I do. ECM is grounded on battery. And there is no resistance in the wires.

[@henrietta70]

@@ScottHadzik Transistor inside the ECM?

[@ScottHadzik]

Send me the diagram [e-mail]

[@henrietta70]

@@ScottHadzik Sent you an email.

[@adalbertopavon3343]

Thank you so much for your help . it help me out alot bless yoy

[@MegaRyad]

can you upload more videos like this please ? with diagrams , this is very high quality video thank you

[@neriofernandez6666]

clear explanation. from phlippines

[@ADYU011]

May 26 2024 , hello , I have 2006 gmc 1500 Savana 5.3L v8 . How do I check the ECM and the knock sensors voltage ? The power come from the ECM threw wire to Knock sensor. The knock sensor is grounded by it being screwed to the engine block . The reason why I’m asking , because the knock sensor show low circuit.

[@cindyrupe3576]

I have a 2014 Chevrolet Silverado. I have had 3 ecms fail in the last few months. The most recent lasted 6 weeks. No warning. The truck just won't crank until a new ecm is put in. But once the ecm is replaced the truck starts right up and runs perfectly. No corrosion, starter is good, battery is good. Any idea as to why the ecm keeps failing?

[@RixtronixLAB]

Nice info, thanks :)

[@fgamboa1973]

My ECM connector has 3 pins ground going to chassis. Also, 3 pins battery power B+ going to main relay, and 2 pins battery power B+ going to battery. Which one should I test in this case???

[@MakerTools]

Excellent! Thank you...)

[@josmith5155]

Hello Scott, Would you have a recomendation for the best electrical auto diagnostics book that focuses on being a field manual, rather than theory, for someone who already has a decent enough auto electrics background? Thanks alot.

[@marcbrett7313]

i did the voltage test and there was a consistent 12.36 volts on the ecm.how do i diagnose a bad ecu? my motorcycle does not power up.any help or advice you could provide?.thanks

[@IMPORTANTVIDEOS7]

@@jordanammanshmesani whatbdo ya mean ground to ground? In the ecm?

[@phil8500]

Hello I have Toyota auris which we know ECM control ground . I get o2 sensor fault which didn't fix after replacing the o2 sensor . ALSO AFTER around 7 min alternator stops charging . (This is almost same time o2 cause engine light to.come on as well) When o closely test o2 sensor and alternator both sharing wires and Ecm stops ground to these component . I couldn't find any broken corroded wire ,however I can see somebody already worked on wires before . Would you plz help me ? how shud I make sure this is ECM ? or anything cause ecm to cut off ground after 5-7 min (or in the word after engine getting a bit warm) ? cheers

[@ScottHadzik]

Test between ground pin of the ecm and the negative terminal of the battery with the vehicle on. It should be close to zero volts. If it's more than 0.5 volts the ground to the ecm has high resistance.

[@Infinitpossibilities]

Are battery positive always pin one and main ground pin 2 of an pcm / ecu?

[@ScottHadzik]

No, it's not unfortunately. It varies by vehicle. It's possible that the ground is black and the power is red, but that's not really a guarantee either.

[@FarAboveDaCloudz]

If only it was that easy or universal, we would all love life. Also, ECMs nowadays tend to have grounds that are "Chassis" and others that are "Signal". Make a huge difference on what you're looking for. You definitely need to get a proper ECM schematic from AllData or IdentiFix or another very reliable source. It will save you a ton of time and headaches. Good luck.

[@stspringer2003]

Nice video, but you never mention how you had "current" going through the circuit, "by turning the ignition key to the on position" or what a good reading should be, on the dvom, when you connected the red lead on the battery positive, and the black lead on the connector positive pin, with the key in the on position. A good reading would have been zero volts, or close to it, you never mentioned that when the dvom meter showed a 12.6 voltage drop, the same on the negative side of the connector. I did see where you mentioned if it was below .5v that was ok, but you really never mentioned that you were dropping 12.6v on the positive side when it was showing on the dvom. That reading of 12.6v, I am sure confused a lot of newbie viewers, and should have been cleared up that that was a voltage drop reading, and the reading should have been zero volts or close to it ,5v tops. I notice most videos on electronic troubleshooting do the same as what you did, they must assume we know what a good reading should be. Other than that your video was very good and clear. My two cents, I guess I am a nit picker.

[@IMPORTANTVIDEOS7]

Scott can you help me with a ecm i have on a can am atv its blowing 5 amp fuse and i unplugged ecm and its not blowing fuse now. I need to know how do i find out if its the ecm or a short. If i buy a new ecm its 750.00. I need help. i have videos on here also. But im not smart with electrical.

[@ScottHadzik]

The fuse opens when power is shorted to ground. With the ecm disconnected install a new fuse and wiggle the power wire. Check pinch points like suspension and doors. If the fuse opens with ecm disconnected then it's the power wire going to the ecm. If your confident in the power wire then the ecm is bad. A short on the ground side is unlikely. It would have to short to power. Check for melted wires.

[@IMPORTANTVIDEOS7]

@@ScottHadzik thank you so much. I will get a new ecm and see if that fixes it.