Trailer Lights Not Working on a Trailer Towed by a 2002 GMC Yukon XL

Question:

I have a 2002 GMC Yukon XL with factory wiring harness. Tail lights do not work on trailer since the GMC has separate tail and stop lights. I need the parts necessary to make my trailer tail lights work. What do I need?

asked by: Chuck

Expert Reply:

The factory trailer wiring harness on your 2002 GMC Yukon XL should already be converted to a combined system even though the vehicle has separate turn signals and brake lights. Whether it has a 4-Way flat or 7-Way connector, the turn signals and brake lights are combined. You can test this with a circuit tester such as # PTW2993 while someone turns on the turn signals and brake lights.

It sounds like there is a problem in the wiring either on the vehicle or trailer. Make sure both the vehicle and trailer connectors are clean and free of corrosion inside and out. And make sure on the trailer side that the main trailer connector ground and the grounds for all of the lights are attached to clean and corrosion free bare metal surfaces.

I have included a link to our help article that will help you test the vehicle side connector.

expert reply by: Michael H