Troubleshooting Trailer Lights When Some Are Not Working

Question:

The tail lights and about half the running lights are working, but some of the running lights are not working. Any suggestions what would cause this? I have tried replacing some of the bulbs.

asked by: Chris

Expert Reply:

First, you will want to test the trailer connector on your vehicle with a tester like part # PTW2993. I have attached a link to a video that explains how to test the vehicle wiring.

Most likely, the culprit is a loose, corroded, or broken ground. You will want to check the trailer connector for any signs of corrosion or damage and then check each of the lights to make sure they have secure grounds, and the wires have not been damaged.

If you find that the problem is on the vehicle side, you will want to start at the trailer connector and work your way backward to where the harness is connected and look for signs of corrosion or damage or loose wires, and repair as necessary.

expert reply by: Jeffrey L