Only Trailer Side Marker Lights Work After Installing a Trailer Wiring Harness on 2010 Toyota RAV4

Question:

Just finished hooking up wiring harness. Tested by hooking up to trailer and the only lights that worked were the side marker lights. Any suggestions?

asked by: Ron B

Expert Reply:

This sounds like a bad ground either on the wiring harness # 118412, on the trailer or both. First try moving the ground from the wiring harness. Make sure it is attached to a clean and corrosion free bare metal surface. Also make sure that the main trailer side connector is grounded to a clean and corrosion free bare metal surface. Do the same for each of the lights on the trailer. Make sure the trailers connector is corrosion free.

If the trailer has an aluminum frame, a tilt bed, or folding tongue you will need to have jumpers ran from the light grounds to the main trailer connector ground.

I have included some additional links that should help you troubleshoot further.

expert reply by: Michael H