2018 GMC Yukon XL - Heavy Rain issues

[cdtdelta]

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]

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.

 

[Marty_S]

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).

I found a new pothole on one of my ranch roads. THUMP! and carry on. The next day the dash starts throwing blinking lights, 30 chime noises and 2 solid red lights. One for AntiLock braking, another for Traction control and CEL. The only stored trouble code is for MAF but these other codes worry me a bit. How can they NOT be throwing codes? Fairly sure they are related to using old sensor cable on new rotor assy but not positive. It does make me apprehensive on replacing same on drivers side. I definately won't misplace the new sensor cable this time. You can reset all codes by pulling both battery cables and wrapping them together overnight. When you wrap them together make sure metal is touching metal. This will zero out any (all?) error codes and start a new series of tracking. It will also wipe your radio stations, seat and lighting presets and any current error codes. The good, bad and can't think of any ugly consequences unless you have multiple batteries, cable sets and they aren't removed with ends taped so nothing can short. My 86 Suburban was FOLLOW ME rig at Moffett Field. On rear passenger side panel is a wiring junction containing 6 lugs and a warning; WARNING 11,000V. I ended up pulling 2 batteries and 1 alternator then wiring off all ends except 2 on closest battery to front of engine. Still runs although I did sink it and now it has lower end knock.

 

[Bigburb3500]

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).

I’m not super familiar with the newer engines but I had a similar issue on my old Suburban 2500. The MAF sensor was completely shot due to mileage and major abuse. It would do a lot of what you are saying with CEL and every light, that could go on, would flash. Check that and your engine filter. Seem simple but if it only does it while raining, either it’s something getting wet that should not be or it’s likely a fuel/air issue.

 

[ReaperHWK]

Tons of wiring harnesses under the car. My guess is one is exposed and getting moisture in there and causing the issue until it does out. There is also a large harness right above the spare tire that can rub on the frame member and damage wiring. Trust me I know.

Another thing that can happen is a module can get damaged and corrupt the canbus which can cause a lot of systems to get comm errors and it will cause all those messages. To troubleshoot that get a scanner and check for comm fault codes in every module.

 

[Flugzeugfuhrer]

I'm having a similar issue with the 2020 Yukon. It looks like various other models 2016-2019 Silverados/Sierras have a known headlamp water intrusion issue throwing codes and leaving a dead battery/vehicle won't start. I'm getting the same/similar codes: P129D, P1682, P0561, P2535, P0700 all because of wet texas weather. Vehicle won't start (does after leaving it on tender all day). The fix is inspecting the headlamp assembly and connections. Disconnect the headlamp and see if troubles go away. Clean up any connections/repair/replace as necessary. I'll probably be tackling this tomorrow. Don't really want to spend a grand on a new headlamp.

 

[B-train]

This has nothing to add to the thread, but more of a PSA about driving with hazards on in the rain.........STOP doing that! Your running lights are just fine. The 4 way flashers are so h a r d o n the eyes and distracting for everyone following you in the dreary rain spray that gets mixed up.

Think of your eyes seeing bright, then dull, then bright, then dull........on repeat. It's dangerous and tiresome on the eyes and brain. I'm not sure WHO started this phenomenon, but it doesn't help at all. Use the flashers for an emergency, like they were designed for.

Ok, carry on. Soap box is over. Thanks for listening.


Edit: apparently "hard on" the eyes is a bad phrase. LOL. Back to creative writing school....

 

[RoadTrip]

I will add to the thread.

Check those grounding points of wiring underneath the driver’s and passenger’s feet, outside, underneath. Also, check the grounding point on the back of the block by the starter.

Bad grounding will start an electronics circus like the OP described.

Yeah, what’s with the flashers? We all know to slow down in water. Rant over.

 

[Doubeleive]

is that a regional thing? nobody puts there hazards on in the rain, not around here anyway no matter how hard it rains nor how foggy it gets with zero visibility.
the only reason one would put on hazards is if either there broke down or can't move at the same speed as everyone else for whatever reason.......forced to move at a slower pace than traffic... OR there is a accident that just happened and traffic is having to suddenly brake without warning.

 

[Tahoe14]

It is illegal in some states to run with the emergency flashers on.