Troubleshooting Factory Brake Controller Not Working When Using Brake Pedal

Question:

2012 GMC 3500 Sierra dually I have a factory trailer brake on my truck. It works if I manual lay do it but when I just push my brakes it doesn’t work. All connections are good. What can it be?

asked by: Tina F

Expert Reply:

Just to be sure, are the brakes not engaging while you're stationary and pressing the brake pedal? The brake controller on your 2012 Sierra 3500 is going to be proportional so the brakes won't engage unless you're moving. The brake controller has to sense deceleration before it will apply the trailer brakes. The manual override works no matter what. If they aren't working while you're moving then it is likely an internal problem and I would replace it with something like the # 90885.

expert reply by: Robin H