Trailer Brake Controller Applies Brakes with Manual Override Not Brake Pedal, 2003 Chevy Silverado

Question:

We only have trailer brakes when manually applied. Could it be a problem with gove box connection wiring. We have been looking for a wiring diagram for 2003 Chevrolet 2500.

asked by: Max B

Expert Reply:

Since your trailer brakes only work with the manual override, that indicates a problem on the red wire of the brake controller. This wire gets a signal from the brake switch and tells the controller when you apply the brakes.

The port for a brake controller on a 2003 Chevy Silverado is located in a junction box on the driver side on the floor towards the front of the truck. The port on the top row, second from the left is where you would install a connector like # 3015-P. The other end plugs into the back of certain brake controllers or can be cut off and hardwired to the controller.

If this is where you have a harness plugged in, look at the position of the red wire. It will need to be in the bottom left slot if looking at the back of the plug. If it is not there, then that is why the brakes do not work with the brake pedal. You would just have to move the red wire to the correct location.

You will also want to check the CHMSL fuse (center high mount stop light). Check the owners manual for its location to determine if it is blown and needs to be replaced.

expert reply by: Michael H