Troubleshooting 1999 GMC 2500 Brake Lights Not Working with Pilot Brake Controller Installed

Updated 04/18/2018 | Published 04/17/2018

Question:

When i connected the brake controller i lost brake lights on the truck. Now the only way the brake lights come on is when i push the manual override on brake controller. Any idea on what could be going wrong. Reese Pilot Brake Controller on 99 GMC 2500

asked by: Curt T

Expert Reply:

The 4 wires at the back of your Pilot # 80550 brake controller are connected to the following functions:

Black - 12V Power
Blue - Brake Controller Output to 7-Way
White - Ground
Red - COLD Side of Stop Light Switch (only gets hot when brake pedal is pressed)

It sounds like the Red wire doesn't have a clean connection. If your brake lights on your 1999 GMC 2500 aren't coming on when the pedal is pressed but then they activate when you use the manual override lever (which pulls power from the battery) it would most likely be because of a poor connection to the Stop Light Switch.

Inspect that wire and make sure everything is secure and none of the wiring is damaged. Replace anything that looks like it needs it and that should fix your problem.

Let me know if you continue to have problems and I can help you troubleshoot further.