2018 GMC Yukon XL - Heavy Rain issues

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cdtdelta

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Hey all,
I've had a weird issue come up with my 2018 GMC Yukon XL SLT in the last few months. It currently sits at 108k miles. I've had two instances recently where I've driven through a heavy downpour (to the extent that you are driving with blinkers on), and suddenly the check engine light goes on. At the same point it seems like all the systems that show up in the GMC app under diagnostics fail (engine and transmission, antilock braking system, stability control, air bag, etc.) and the transmission starts to misfire. When I've taken it in to be serviced, they can't find anything wrong, they end up resetting the sensors, and then all the diagnostics go green. And the two times this has happened I had different mechanics check it out.
The second time this happened was earlier this week on a drive back from GA (to TX). We took the long way around to avoid Hurricane Francine, but still had some rain from the outer bands (it hadn't made landfall yet). We were about two hours away from home when we hit it and everything went haywire. Thankfully there was a GMC dealer nearby that was able to check it out, but again they just reset everything and it was fine.

My questions are
1) Has anyone ever experienced a similar problem?
2) Is there a way I can do the reset to at least rule it out if there's not an actual problem?
3) I'm wondering if there's something exposed that shorts out or something when there's enough rain, but not sure where to check.

It's only happened with a really heavy downpour. If I'm driving in a "normal" rain storm it's fine, and if the car is sitting in the driveway during a rainstorm it's fine (ex. it was in the driveway for Beryl and no issues).
 

BacDoc

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Apr 11, 2024
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Besides a qualified tech looking at the truck you should try to get rid of moisture. My advice to you is to go on Amazon and buy a case of those Damp Rid packs or similar. Not that expensive and just put them everywhere you can.
Won’t totally fix your problem but it help. They pull moisture very well and if you find one that is full of water it can help you diagnose.
 

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