Brake Controller Does Not Sense Trailer Connected to 2012 GMC Sierra

Updated 11/17/2015 | Published 11/16/2015

Question:

I had this controller hooked up in my 07 Sierra with my current trailer...worked fine, just switched the controller over to my 2012 Sierra, same trailer and now the controller doesnt sense the trailer for applying the breaks. All trailer lights work as should, and the truck disables the park assist, so it knows the trailer is there, but the brake controller will not show any numbers, or apply brakes at all. I wired it up the exact same as in my other truck.

asked by: Andrew

Helpful Expert Reply:

There are a few common issues associated with GM trucks and brake controllers. First, you may need to make some connections under the hood to make everything fully functional. It is possible that the brake controller blue output wire does not go all the way back to the 7-Way connector. I have included a link to a help article and the latter half of the article explains these connections under the hood of your 2012 GMC Sierra.

Also, make sure that you have the brake controller wires connected to the proper tow package wires under the dash of your truck. The truck red wire goes to the controller black wire for 12 volt power. The truck dark blue goes to the controller blue for output to the trailer brakes. The truck light blue (or orange) wire connects to the controller red wire for input from the brake switch. And the truck white wire connects to the controller white wire for ground.

Also you can make sure that the truck and trailer side connectors are clean and free of any corrosion inside, where the wires attach, and outside on the pins.

expert reply by: Michael H