Trailer Brakes Disconnected

There is a service bulletin out for 2024 GMC brake controller module and the dealership installed the new one.
On our day 2 trip, check brakes manually, no brakes on trailer and had a message on screen Trailer Brakes Disconnected - Service Trailer Brakes. We hooked up to our friend’s Ram truck and the trailer brakes worked. Also had a mobile tech out who confirmed that the amperage to the trailer is correct, so it seems to be a pickup issue.

So far we have tried:

  • disconnecting the solar
  • disconnected the black wire power feed between truck battery and trailer batteries
  • someone suggested adding a Furrion camera plug adapter - that didn’t work
  • tried connecting to the 7 pin in the bumper

Has anyone had this problem and what was the fix?

Someone said GMC’s preliminary SB said to use a CURT 7-pin adapter with resistors in it - anyone know if that will actually work? Have also had a suggestion to add a heavy diode?

1 Like

Rudy - I had the same problems with my brand-new Brinkley and 2024 Sierra 3500. For brevity’s sake, I’ll omit all of the details, but we were experiencing constant trailer brake disconnections. I had the GMC dealer replace the brake controller module per SB #23-NA-149, and haven’t had a problem since. Pulled the trailer several hundred miles through Colorado and Utah, plus in and out of storage - flawless.

Is it possible your dealer installed the wrong/same module? Should be marked with PN 23306694.

I’ve not had to do anything involving resistors or diodes, nor have I made any mods to my camper for this issue.

Good luck, and please let me know if i can provide you with further information.

I have had the same problem. We just finished our first run. 40 miles into the trip. We started getting a check trailer wiring error message on our Silverado 3500 Duramax. The alert keeps popping up no matter how many times you dismiss it. We pulled over and made sure the trailer wiring was intact. The braking seems to be working appropriately as well as all of the brake and turning lights. The error message was incessant and became very annoying. I see that this has been a problem for some time especially with GMC/Chevy trucks.