Troubleshooting GMC Envoy Brake Lights Not Functioning After Connecting Trailer

Question:

I had a trailer hooked up and everything was working. Then all the sudden I had no break lights. Not even on the envoy. Even with the trailer unhook. I still have no break lights. And I have checked all break fuses that pertain to break lights

asked by: Jerry

Expert Reply:

If your Envoy brake lights stopped working along with the trailer's brake lights and you know the vehicle brake circuit fuses are good then the issue is likely to be related to the connector for your wiring harness.

The 4-pole and 7-way harnesses for your Envoy, such as # C55384 and # 74682, use a round U.S. Car type connector to join the vehicle wiring. There could be trapped moisture, foreign material, corrosion or a bent pin that is causing loss of the brake light signal. Bad corrosion could cause a short on more than one circuit.

I suggest you unplug the trailer wiring and then try the vehicle brakes to see if removing the harness solves the issue. If so then replace your trailer wiring with either a new 4-pole or new 7-way. You can refer to the linked article for help in troubleshooting your wiring.

expert reply by: Adam R