Troubleshooting Right Side Trailer Running Lights Not Working With 2016 GMC Sierra 1500

Published 04/19/2023

Question:

I have a 16foot sierra 1500 and I dont have running lights on the right side of trailer. I do have brake and turn, but the light is not as bright as the other side. I installed a new brake light and new wire from light to connection plug, same result. I also installed new plug connector on the truck. Please help

asked by: Eric W

Expert Reply:

If you haven't already checked the ground connections I would go ahead and start there. Between the running lights not working and the other lights being dim that is a good bet. Make sure they are secure on a clean, bare-metal surface. If that is not the issue we can start some testing.

Using a circuit tester like the # PTW2993, check the connection at the rear of the truck for power. If you have power here, check the trailer connector and the wiring again. If you don't have power then you know the problem is on the vehicle side.

If it is the vehicle side go ahead and check your fuses. I'm assuming this is factory wiring, and the fuse locations should be listed in the owner's manual as well as inside the fuse box lid. If the problem is not the fuses then it is probably a short in the wiring. Work your way back using the circuit tester and repair as needed.

expert reply by: Robin H