2010 Tahoe LTZ electrical saga, need some input... - SOLVED

Quick update (idk about anyone else, but I absolutely loathe when I'm reading through a thread on a similar problem to what I'm chasing and the resolution was never posted or the saga just stopped at some point. So I'm trying to be diligent about seeing this through on here.).

Literally only a few miles after my last post, the problem recurred. So I threw my hands up and took it to the new (third) shop.

This guy is an electrical guru and is THE go-to guy in town for any automotive electrical issues, particularly on GMs. No one I talk to has EVER seen this guy fail to diag an electrical issue in the last 20+ years he's been in business. Multiple other shops in town send stuff to him.

(Funny story, he also mentioned that he JUST took a refresher/update course on domestic CAN bus systems and diagnostics. Lol.)

He's had it for two weeks and we've got no word, which has me worried because I know he started working on it only a couple of days later.

I'm about to start praying to gods I didn't even know existed.

I'm guessing a bad module that freaks out and makes noise when it feels like it..
May take some time, being as intermittent as it has been.

Since you say the TCM is reporting the error, I wonder if it has anything to do with the connection order..
Looking at this chart, the ECM and BCM are next to the TCM.. I think..
I'm going to say BCM just because the ECM's are known to be pretty solid.. (wild guess, don't take me seriously)

Well, another week later and the best of the best in this area can't figure it out.

We had had a phone conversation a few days ago where he was pretty suspicious of the BCM and was waiting on another failure to confirm. But I guess very shortly thereafter, he identified another ground...one shared by all the modules...that showed major signs of arcing; wires at the crimp were pretty corroded and the ground itself was scored all to hell.

So he fixed that ground and it didn't fail again on him all weekend, so he called us today to come pick it up and give it another few-hundred-mile test run just in case.

Unfortunately, we didn't even make it out of the parking spot, lmao. Wife started it up and it had the exact same failure.

So yea, the saga continues.

Part of the problem is that while the failures are becoming far more consistent, it still won't stay in that state long enough for him to actually test the buses. Which is kinda weird.

I appreciate that he's sticking with the proper diagnostic process, but man I really just wanna start slapping new modules in it one by one at this point lmao.

I hate reading about these issues..

Luckily you didn't make it out of the parking lot!

Hopefully your guy will spot it soon..

Well, we're trying the whole "test drive" thing again this weekend, lol. Made it out of the parking lot and on a few errands this time at least. Whether that's good or bad at this point, idk.

He wouldn't tell us what he did this time and says he "has his doubts", so at this point I think he's trying to anti-jinx himself, haha.

What drives me insane is that we love this thing so much and it's in no way worth giving up on. It's getting up there in mileage because we use it for business purposes, but it's fairly clean and we've taken good care of it. (It came to us with that little dent in front of the driver door, but otherwise there's barely a scratch on it. Interior and engine bay are still really clean too and the thing runs GREAT outside of this issue. Have barely had any issues.)

The fact you said it happens after you drive it, still makes me think of a heat-cycle issue. Something like a connection in the transmission or a cracked solder joint in the BCM. Once the circuit loads up, it warms up and the gap opens and loses connection.

I would reset the codes, let it cool overnight, then drive it and as soon as the first code pops up, shut it down immediately if possible...be careful doing this with regards to steering wheel lock. Then take a scanner and see what codes are populated. You might get all of them, but you may get lucky and have only one or 2 which might help pinpoint it.

Doubeleive said:

logic to me dictates that if the code is lost communication with ecm, then perhaps the problem is the ecm and you do not indicate that this was replaced.

Click to expand...

I forgot to add this.

Given the proximity of the PCM to the engine, also could point to a heat-cyxle issue. Definitely worth a try to swap a PCM.

Might have been a misunderstanding, but the mentions of mileage and such are just the general interval between incidents, not consecutive driving miles all in one shot immediately prior to failure or anything.

It's done it a couple times while running, but mostly does it on startup. Has done it pretty evenly on both warm startup (recently driven) and completely cold startup (hasn't been driven, engine is cold-soaked). (FWIW, it's also done it in 25°F weather and 75°F weather, dry and wet, etc.).

There's no real rhyme or reason to it other than a previously consistent (but now steadily declining) amount of time in between failures. Regarding that time, we're not sure if it's mileage, runtime/drive cycles, or just starts that's causing it because they're all pretty directly related and our usage is very stylistically consistent.

I can say that it has done it to the mechanics it's been to as well, with fairly similar erratic patterns/runtimes.

To your point, the guy who's dealing with it now has mentioned he's most suspicious of the BCM (and possibly the ECM), but he's been sidetracked by a couple possible/apparent issues that he wanted to fix/try first (for example, the ground the was clearly arcing out, lol).

I will say that once we figure this out, this thing will probably never have an electrical problem again with all the grounds and such that we're fixing along the way lmao.

Anyway, like I said we're test driving it on a "mystery" fix (lol) so I guess we'll see if it's even still doing it over the next few days and go from there.

Does it have a worn engine mount? If so, the engine could lift on the LH side working that ground strap to the firewall. Not likely the issue but wanted to toss that out.

You guys are never gonna believe this.

OnStar.

That's it. That's the problem. Lol.

More specifically, the VCIM or OnStar Modue. As with most of the other modules we've been suspecting, it's on the high speed lines...so when/if it goes, everything goes.

I don't know what led him down that path, but dude bypassed it and it's been fine ever since. If/when we ever want OnStar we'll obviously have to replace that module, but it's not really consequential so we're leaving it bypassed for now.

I don't know whether to laugh or punch air, but there's the long-awaited solution!

DamThatRiver24 said:

You guys are never gonna believe this.

OnStar.

That's it. That's the problem. Lol.

More specifically, the VCIM or OnStar Modue. As with most of the other modules we've been suspecting, it's on the high speed lines...so when/if it goes, everything goes.

I don't know what led him down that path, but dude bypassed it and it's been fine ever since. If/when we ever want OnStar we'll obviously have to replace that module, but it's not really consequential so we're leaving it bypassed for now.

I don't know whether to laugh or punch air, but there's the long-awaited solution!

Click to expand...

onstar for these has been offline for a while now, so you couldn't use it even if you wanted to. It sunset with 3g

Doubeleive said:

onstar for these has been offline for a while now, so you couldn't use it even if you wanted to. It sunset with 3g

Click to expand...

Lmao I had no idea; this was the first GM vehicle I'd owned in roughly 15 years and we never even looked into using it.

Well I guess that answers that even further, haha.

Glad you got it fixed. Like I mentioned mentioned prior in this thread bad modules are notorious to corrupting all coms and causing random/weird errors.

It’s best to start unplugging suspect modules one at a time until the problem “goes away”.

Wonderful news!

So glad I ripped mine out already...one less module to worry about..

I wonder if it could have been fixed by pulling the fuse, or if it was a bad joint randomly losing connection..

Removing a module may be a solution, but if the network goes through the module you'll lose comm with any other modules that are downstream. It depends on how the network is wired.

Yep, the onstar is one of those modules.
If removing, you must jumper the network cables. (tan = tan, tan/blk = tan/blk)