Troubleshooting Trailer Brakes Not Working with New Brake Controller on GMC Sierra

Question:

I have 2011 GMC Sierra the brake controller on my trailer worked fine for 4 years. Now I can not get brakes to work, bought new brake controller still same problem. I do have power on red wire. I also have power on manual brake. But brakes click on and off do not lock up. I have no power to blue wire when brakes are pressed.

asked by: Scott M

Expert Reply:

The first thing you will want to look at with the new brake controller is how exactly you are testing it. If it's a proportional controller like the Prodigy P2 # 90885 and the truck is sitting still, it's going to send back very minimal power (if any) back to the 7-Way via the blue brake output wire when the brake pedal is depressed. This is because the controller sends back power proportionate to the vehicle's deceleration rate.

This means with the truck sitting still you likely won't get power on the blue wire when pressing on the brake pedal but you should still get full power there when using the manual override.

If you take the trailer on a short test drive around the neighborhood or a nearby parking lot and the brakes still don't seem to be activating when using the brake pedal then I recommend turning your attention to the trailer side. Since the same issue has happened with 2 brake controllers (one brand new) then there may be an issue with the brakes themselves or the wiring leading up to them. Inspect any wiring you can gain access to and check for any exposed or pinched areas that need to be replaced. Also check to make sure the ground wires from each of the brake assemblies are still securely attached to a clean, bare metal surface on the frame that's free of any corrosion or debris.

If this does not resolve the issue please let me know and we can continue to troubleshoot.

expert reply by: Chris R