2019 Yukon XL Denali wifi issue following body repair

mruby · November 9, 2021

We got in a rear end accident this past summer. We have subscribed to onstar premium with unlimited data, and it has always worked for us, until we picked our vehicle up from the body shop. We didn't notice it right away but a couple of weeks later we went out of town on a road trip and could not get the wifi working. We've had a number of calls with onstar, they've done everything they can on their end. We took it back to the body shop, and they scanned for error codes, and couldn't find any. They said we'd have to take it to the dealer so they can scan with their special diagnostic stuff. We did, it cost us 100 bucks for diag, and I was told that it is the "Telecommunication communication module" or "TCM", and that it would cost us 900 bucks to replace (in addition to the 100 we already paid). I was hoping this could somehow be tied to the accident/repair, but they said this module is under the dash, not even close to the rear lift gate that was replaced.

I asked the dealer if they checked the fuses, or if it could just be in need of reprogramming, they said no. But i don't have a ton of confidence that they check this kind of stuff. Dealers seem to be trigger happy with just replace all the stuff till it works again, cause its easiest/cheapest for them.

Does anyone have any experience with this, or know what part the tech is talking about? When I lookup a TCM, I see transmission control module. It sounds like he is making stuff up to me. But then I have a general distrust for dealers.

Thanks!

Russ Swift · November 10, 2021

1. Agree re dealers.

2. Go back to your body shop, or any body shop you know or trust, and ask them who they use to check/repair electronic issues, who’s their electronic go-to genius.

3. Then have the electronic specialist check it out.

4. I had to have the rooftop antenna replace to solve a problem with my system (2016 GMC Yukon XL Denali). Seems there was a water drain gap at the top end of the gasket that let water in vs let it out. Not sure when, but that design flaw has been changed now to the gap at the bottom end of the gasket.

5. Even if it’s not the antenna, find an electronics specialist to get a straight answer.

Good Luck, Stay Safe