SOLVED - Big 3 upgrade, EVERY warning light on immediately after.

petethepug said:

ARES Technologies No1 Reman Pre-Programmed Engine Computer PCM ECM ECU

If you need an engine computer, we are here to help you to identify the right module for your car.

arestechnologies.com

$129 for a new BCM coded to the truck.

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I think that's the most logical course, at this point... The other terminating resistor is built into the BCM for these guys, isn't it?

Any updates? My hat's off to you in your persistence in continuing to troubleshoot. I am hoping that you have resolved the issue and have just been too busy enjoying your vehicle as it should be to be posting on here.

Thank you for your kind words, Speck!
Unfortunately, no solution thus far.

I'm still driving it every day, although I've been more and more annoyed with this issue as a result.
I pulled the underhood UBEC, blew it out with compressed air, sprayed it thoroughly with contact cleaner and let it sit until it thoroughly dried. I inspected each and every connection, checked every fuse for continuity, and re-seated them for a second time just to be thorough.

I still see ~120 ohms at the DLC, although I've ruled out the rear terminating resistor already. I have yet to try a different ECM (next on my list), however I did replace the BCM with a programmed unit to no avail - I was able to return it, so that was fortunate.

I went against my better judgement and threw OEM power and ground wires back on for a day - apart from annoying me and eating up more time, that was also a bust.

The entire high-speed channel is out, so the termination is the most likely cause in my opinion... The only thing that truly ISN'T functioning is the ABS itself. That wouldn't explain the other modules presenting U codes, however... I wish that it were feasible to simply tear the ECM apart and replace the resistor, that appeals way more to me than throwing $3-400 darts at a board...

I'm too stubborn to call it quits, so I'll figure it out eventually. I just may be in for a rough winter in the meantime!

Have you tried disconnecting the ABS unit to take it out of the loop and see what happens? Maybe try pulling the fuses first.

You could also try removing all power again. Power down your dash cam or whatever is hardwired in. Touch the positive and negative cables together and hold for a few seconds. This will drain the capacitors in the computers. Honking the horn with the battery disconnected can do the same thing too.

Power back up with positive cable landed first, negative last. Turn on the key without starting and just let stuff wake up. Not sure if this will help, but sometimes a hard power cycle can be beneficial.

I have; unfortunately, each individual module (I tried all of them, individually and together) yielded no effect.
I definitely appreciate the suggestions, nothing is too silly to try at this point.

I think I'm at the "buy an ECM and hope it works" point, considering the consistent ~120 ohms at the DLC. Improper termination is the only thing that makes sense to me, given the parallel nature of these systems...

I just thought of something... does GM use the ABS module as a gateway for the other modules? If so, that might explain a failure to communicate, despite the parallel nature of their functionality. If the CANBUS itself isn't parallel, but the power to each module is, that could potentially explain them failing to communicate but functioning otherwise - at least that's what I'm wondering now.

Pine Hollow Auto Diagnostics channel on YouTube has a pretty cool series on an Avalanche with bad class ii network and his troubleshooting steps. Think it has “parts cannon” in the title. Works his way through all the modules with a pico and test lights. Might give you some insight on the various systems and relations. Good luck.

Edit: it was a Suburban. Here’s part 1:

I'll give it a whirl, thank you!
The part that drives me the craziest here is that it runs and drives, w/ functional 4WD... yet ALL hi-speed canbus modules fail to communicate.
If it was a lawn ornament, I'd have probably figured it out by now

mattbta said:

Pine Hollow Auto Diagnostics channel on YouTube has a pretty cool series on an Avalanche with bad class ii network and his troubleshooting steps. Think it has “parts cannon” in the title. Works his way through all the modules with a pico and test lights. Might give you some insight on the various systems and relations. Good luck.

Edit: it was a Suburban. Here’s part 1:

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It may have been the Esky you were thinking of: