Troubleshooting Curt Brake Controller Installation in 2007 GMC Sierra New Body Style

Question:

Hi, Why am I getting a constant 12 V at the bumper plug? Key on or off does not make a difference. I have the curt controller connected. Unplug the controller and 0 VDC

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Expert Reply:

First I suggest making sure you are testing the brake circuit pin on your Sierra's 7-way trailer socket. If you refer to the linked photo of a trailer connector you will note the brake controller's output is carried on the pin at the 5:00 position; the ground is at the 7:00 position.

If you happened to test the 12V auxiliary power circuit, carried on the pin at the 2:00 position, it will have power at all times.

I see that you purchased Curt Universal Wiring Adapter # C51515 which installs via hardwiring. It is possible the red input signal wire is connected to the wrong wire. This red wire needs to connect to the COLD side of the switch, to the wire that carries +12V ONLY when the brake pedal is pressed and at no other time. In your truck this should be a light blue or orange wire as noted in the linked article which explains brake controller installation in your truck.

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Adam R

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