Does the topper have a high mounted brake light? I can only make the wildass guess that they tapped the wiring harness for something like that and freaked the towing system out (since it has the integrated lighting check).

I would try to disconnect their harness and see if it clears the error. It should be a plug for removal of the cap unless they're total hackers.

 

X2
I think I remember owners having issues when tapping into brake lights for tailgate light bars. These trucks have so many self checks you can't do stuff the old way anymore.
Remove the connection and go from there.

 

My guess is he tapped the trailer system wiring instead of a tail lamp.

ALL trucks now a days are picky as hell with plugging/tapping things into trailer systems. They all generally use a electrical component called a Pulse Width Modulation. I've yet to encounter a trailer system that plays nice unless people start adding resistors, encoding boxes, or converters (like CURT for example).

I'm 100% your dealer tapped the trailer system and not a tail lamp.

My camper lights would not function properly at all when plugged into the trailer system (all kinds of bizarre oddities and dash errors). I ran into this problem once before so I knew what to do; tapped everything in the rear lamps and now it works flawlessly.

Good news, once you remove that trailer tap the errors go away.

 

A lot of times accessory installers will use those little piggyback tapping clips and it’s possible to completely cut a wire using them. I would bring it back to the cap installer. They need to fix it.

 

Hello. 2024 LT with advanced trailering pack.

Had a ARE topper installed. Verdict this out on quality. Giving topper dealer time to fix leaks and unglued sliding window. More later.

Get this error message at startup: "Trailer Brakes disabled - Service required."

Topper dealer said it will go away in time (been two weeks) or go to dealer and get error cleared.

Pretty sure it won't be covered under GM warranty and will need to pay out of pocket.

Any idea what is causing this and fix?

Thanks.

You could try pulling the battery negative and see if that clears it, but my guess is they used a scotch-lok to tap a wire for power that they shouldn't have.

V=IR is heartless (Voltage = Current * Resistance) and they added the resistance of another circuit to a wire with a resistance probably precisely calculated and compensated for with the BCM of the truck.

 

They incorrectly tapped into trailer circuit, my Leer dealer had to run all wiring up to fuse block under hood.

 

An easier way to have them do this correctly is to buy the adapter that plugs into the trailer wire harness underneath the bed and gives them a wire to correctly use for the brake light in the topper.

 

That is still tapping the trailer wiring circuits. My utility trailer had a 7 way plug since 3 of the 4 trucks that would be pulling it had 7 way hook ups. But when plugged to my 24 Canyon nothing worked because trailer doesn't have brakes. Switched it to 4 way plug and everything worked as it should.

 

Good gouge everyone. Thank you. I didn't want to deal with the dealer until I knew what they installed was correct - and it appears they didn't.

 

Update.

1. Disconnected camper - no effect. Same error.
2. Disconnected neg battery for 15 mins. - no effect. Same error.

Here are pics of the wiring for the third light. Found a razor blade under the floor mat.??

 

Just noticed. The green and brown are switched on the module. ????