Troubleshooting Brake Controller Installed in 2004 GMC Sierra that Only Works with Override Lever
Question:
I have a 2004 gmc sierra sle 1500. I am using a reese pilot brake control box. I used the wire harness plugged it into my truck and the box and everything worked great for the last 4 years. Now the box shows that everything is connected correct but no brakes when I press the brake pedal. But my brakes work when I use the override. When I checked the harness wires I clipped on to the black wire and the red white and blue all show power. When checking the truck plug the black shows hot and the open spot right next to it shows hot but no wire is there. Nothing changes when the brake is pressed
asked by: Kenneth K
Expert Reply:
Check your third brake light fuse. This is a very common issue on your 2004 GMC Sierra. When the third brake light fuse blows it takes out the stoplight circuit for the brake controllers. You can also easily confirm this by checking to see if the third brake light on the cab of your truck is working or not.
