Trailer lights stay on when engine off-2021 GMC Sierra

[driftwood1]

Trailer lights will not go off even after 10 minutes after engine shutoff. Cleaned the connector (sanded the slots and used electronic cleaner), issue persists. I connected to another vehicle, and works fine, which tells me issue is on the truck side. I suspect something in the sophisticated trailering technology. I do have the transparent trailer camera, and it works fine.

Anybody else ran into this issue?

[wulfraat]

When this happens, is the vehicle fully powered down / key fob located outside and away from the vehicle?

Or in other words, is ACC on or is power on in the vehicle when the lights stay on?

This link may help.

https://gm-techlink.com/?p=12721

(love how in this tech article GM took the liberty to re-brand an airstream. )

[LNBright]

I have the problem that I forget to turn on the running lights in daylight: they aren’t on when simply plugged in, you have to turn the headlight control off of auto to park to get them to come on....

Could it be, the park lights are being left on? Just turn it back to auto?

[driftwood1]

I did some more testing on my light situation, to no avail, trailer lights stayed on with:

- headlights on auto and on off
- truck off, locked, and key fob far away from truck
-cleaned connecter and pins again, and with baking soda
- wiggled connector around a lot

I connected my truck to my boat, which is wired with a 4-way flat and a round adaptor, and same thing, trailer lights stay on. When hooked to the boat I did get a running light problem prompt on the trailering app, and it even highlighted the problem pin (the one in the 1 o'clock position). But that error message does not show up when hooked to the Airstream.

I then connected another vehicle to the Airstream again, and the trailer lights went off properly. So as I surmised before, the problem appears to be in my truck, either in the technology or the female port where the connector plugs in. Not sure where to go from here, any advice welcomed. I sure don't want to have unplug my trailer every time I stop to get the lights to go out.

[LNBright]

I have not; my 2020 Sierra does not have the transparent trailer bits, just the in-dash app that can monitor your tires, check your electric connections... (I take it, running the test, everything is working?).

I'd have to see what the dealership says about it....

[LNBright]

I realize yours is a 2021, but I did come across this for reference, might help when discussing with the dealership:

https://www.gm-trucks.com/have-a-201...-gm-has-a-fix/

[driftwood1]

Thanks LN, I had not seen that particular bulletin. When I called the dealer the other day he said they had heard of the flashing lights issue but did not have a fix. Even though mine do not flash but stay on, could be same root cause (trailer pulling more amps than truck module allows). But issue happens on my boat trailer too which only has two Led tail lights, so doubt it is pulling more than 9 amps. I will send this to them and see what they say. Thanks.

[wulfraat]

Originally Posted by driftwood1;

Thanks LN, I had not seen that particular bulletin. When I called the dealer the other day he said they had heard of the flashing lights issue but did not have a fix. Even though mine do not flash but stay on, could be same root cause (trailer pulling more amps than truck module allows). But issue happens on my boat trailer too which only has two Led tail lights, so doubt it is pulling more than 9 amps. I will send this to them and see what they say. Thanks.

Could be it. From the TSB in the link above:

That high voltage may also illuminate LED lights despite trailer theft deterrent not being active.

[rickmc]

driftwood1 - I've got the exact same issue on my 2021 Sierra 2500 HD. Pulling my FC 27 FB no problems until about 5k miles into a trip. Then Airstream marker and tail lights would only go off if I unplugged the trailer. The truck spit out the messages below. I also received a diagnostic message that pin 3 was culprit. Stopped at GMC dealer on the road home. Using a scan tool plugged into the 7 pin hitch he received a red "LT" indicator. Unfortunately he could not get me into service for a few days. I plugged it back in and headed home.
Made service appointment at local dealership. Could not find any issue. Got home plugged it in to trailer. Boom - original issue back. Unplugged truck. Backed Jeep up to AS and plugged in. All lights function on AS as normal. It's the truck.
Got a follow up appopintment with dealership next week. I think there is a short in the 7 pin receiver wiring or in the trailer system module.
I'll advise as to what's going on.

[ROBERT CROSS]

Isn't AS stuff fun?...bright side, they do go off and don't prevent Stream'n.

Bob
🇺🇸

[aftermath]

Originally Posted by ROBERT CROSS

Isn't AS stuff fun?...bright side, they do go off and don't prevent Stream'n.

Bob
🇺🇸

It isn't AS stuff, it is TV stuff and yes, lots of fun to be had here.

[ROBERT CROSS]

Originally Posted by aftermath

It isn't AS stuff, it is TV stuff and yes, lots of fun to be had here.

Yes but... without the AS it disappears.

Bob
🇺🇸

[driftwood1]

Rick, GMC dealership said the trailer light control module on the truck was bad and replaced it under warranty. Solved my problem, so have them check that. They had to put it on lift to access it.

I hope that fixes it for you.

[rickmc]

driftwood1- That's fantastic! I'll make sure I force the issue. Can't wait to start "streaming" again!! Thank you for the follow up.

[subfan1]

We have the exact same problem on our 2019 Sierra Denali. Half way into our three week trip the running lights come on when plugged in. I made an appointment with my dealership as well. I did a google search and it seems to be a common problem with these generation trucks unfortunately.

[Trailride]

Same
Just had that module replaced last week on my 21 Duramax under warranty. Module was on back order for several weeks.

[driftwood1]

Yes, my module took over a month to receive (on back order, like so many things these days).

[subfan1]

I just had the module replaced on our 19 1500 Denali. It took about a week to receive the part. Interesting write up from the tech. Has anyone else have the following done?

Replace module and splice on new lead to pin 25.

I haven’t read about the splice from anyone here. Something new?

[Rosey Jet]

2021 GMC 1500 brakes. I have been having the same problem for a year now and also there is dramatic pulsing of the brakes which I assume has something to do with the controller. Airstream Utah has reviewed the brakes 2.5 hours worth and found no problems and they pulled my trailer with a Ford and did not have the same issue. Has anybody else had Problems with the GM product?

[subfan1]

Originally Posted by Rosey Jet

2021 GMC 1500 brakes. I have been having the same problem for a year now and also there is dramatic pulsing of the brakes which I assume has something to do with the controller. Airstream Utah has reviewed the brakes 2.5 hours worth and found no problems and they pulled my trailer with a Ford and did not have the same issue. Has anybody else had Problems with the GM product?

Hi we have a 2019 Sierra Denali and the trucks built in brake controller works as it should, very smooth. We did have problems with our 2019 23International since new with pulsating braking. After numerous dealership attempts to fix and after two years of awful braking Dexter was notified of our problems and they agreed to have four each whole brake assemblies including drums replaced under warranty. The truck and trailer now stop smoothly.
By the way after the sensor was replaced and the added splice to the truck, it did not fix our rear camera problem so we continue to use the adapter in the umbilical plug to the truck. I now know this problem is on 2019 GM trucks.