2021 Yukon Denali trailer light issues

[dadawson74]

I have a 2021 Yukon Denali and when you connect any trailer to it the right turn signal doesn’t work. We have checked the 7 pin for dirt etc and the fuses. Any thoughts on what it could be. Thanks!!

 

[JKeller]

First I would wiggle the plug some with someone watching the turn signal. If you get any response while doing this, you know it's an issue with the connection.

If you know how to use a tester, that would be my next step on the truck. If it tests okay, you know you've got a trailer wiring issue. If you don't know how to use the tester or it fails the test, I'd open the manual, find the fuses for the trailer lights, and start inspecting them.

Good luck. Trailer lights are a simple thing but I've been down this same road as you and you can spend a lot of time diagnosing and fixing temperamental trailer lights.

 

[jforb]

nvm

 

[Toy Tow Denali]

we get these notices when we plug the trailer in. Says rear light or a turn light or something isn't working. I get out and check all the lights and finding they all work, just ignore the notices and move on...crummy way to run a railroad.

 

[tagexpcom]

I have a 2021 Yukon Denali and with a "Trailering" app to verify trailer running lights, brake, and turn signals are working.

But I don't see a "Diagnostic" screen on my rig - how does it come up? and do you have a "Trailing" app / does it work or show the issue?

 

[JKeller]

I have a 2021 Yukon Denali and with a "Trailering" app to verify trailer running lights, brake, and turn signals are working.
View attachment 427941View attachment 427942

But I don't see a "Diagnostic" screen on my rig - how does it come up? and do you have a "Trailing" app / does it work or show the issue?

On my 2018 F150, I had a "diagnostic" function like you describe - it would literally tell me that each light and function was working, or it would identify the problem. These Tahoes/Yukons do not do the same thing (at least as far as I can tell). Instead, the Tahoes/Yukons have the "Light Test" in the "Trailering" section of the computer like your screen shot demonstrates. That Light Test simply cycles all the lights (turn signals, brakes, night running lights) on repeat to allow you to exit the vehicle and personally observe each light works.