Really Odd Power Problem

[Recks]

So, I’ve had this issue about 6 times over the last 3.5 years.

2018 Sierra 5.3, 6spd, base.

I turn the key, engine starts but then the following warnings show up on dash; “Service Trailer Brake System”, and “Power Steering” warning. I can put it in Drive but not in reverse. I can drive fwd but it won’t go out of 1st gear. No power steering, no tach, no speedo, no OP gauge, no temp gauge, no auto headlights. Traction control light on. I can shut it off and on multiple times with no change. 
When it does this, I usually just walk away for 15 mins, try again and it works fine. 
No codes are saved. Dealer has done a ton of troubleshooting and can’t find anything.

I do have an aftermarket remote start. I don’t know if that matters but it could be. 
Anybody have experience with this?

[rav3]

Search Youtube for your issue. I have seen several videos on water intrusion via the roof shark fin, that travels down to the Towing module on the dash. Pull the fuse cover panel on Drivers side & look for any rust behind the fuse panel. Also, a bad control unit at the back of truck under the bed can corrode and cause issues.

(15) 2017 silverado trailer brake system warning - YouTube

[Recks]

38 minutes ago, rav3 said:

Search Youtube for your issue. I have seen several videos on water intrusion via the roof shark fin, that travels down to the Towing module on the dash. Pull the fuse cover panel on Drivers side & look for any rust behind the fuse panel. Also, a bad control unit at the back of truck under the bed can corrode and cause issues.

(15) 2017 silverado trailer brake system warning - YouTube

Thank you for the reply! I will investigate that today. Much appreciated,

[GMCustomerService]

On 4/7/2023 at 12:18 AM, Recks said:

So, I’ve had this issue about 6 times over the last 3.5 years.

2018 Sierra 5.3, 6spd, base.

I turn the key, engine starts but then the following warnings show up on dash; “Service Trailer Brake System”, and “Power Steering” warning. I can put it in Drive but not in reverse. I can drive fwd but it won’t go out of 1st gear. No power steering, no tach, no speedo, no OP gauge, no temp gauge, no auto headlights. Traction control light on. I can shut it off and on multiple times with no change. 
When it does this, I usually just walk away for 15 mins, try again and it works fine. 
No codes are saved. Dealer has done a ton of troubleshooting and can’t find anything.

I do have an aftermarket remote start. I don’t know if that matters but it could be. 
Anybody have experience with this?

This is certainly not what we like to hear, Recks.  Please know, customer satisfaction is extremely important to us. Our team would be more than happy to take a closer look into the concerns with your 2018 GMC Sierra. To do so, please send an email to [email protected] with ATTN: Recks/GM Trucks in the subject line.

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[14LTZ-1LZ]

Have you checked your battery connection? Especially the negative cable, follow the connection to the frame clean, and reinstall. They will not find any codes like you said "no power". It's like unplugging the battery and installing it again. Basily it's clearing any codes saved. Does it ever ask to roll the window down and back up again? Check this video out, also check the ground on the pillar underneath the speaker on the dash by the driver's side. Search youtube for g218 ground. Good luck.