After Installing Trailer Wiring Harness on a 2006 Toyota Highlander Sport Trailer Lights Do Not Work

Products Featured in This Question

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(294)

$55.06

Hook Probe Circuit Tester

(55)

$11.68

Question:

I have checked all connections and all are correct. The lights on the trailer do not work. I checked the trailer with my truck and it works fine. Is there something else I should do in the car to make this work?

asked by: Dale E

Expert Reply:

There are some things you can do to determine if the issue is on the harness, # 118413, or somewhere else. First, make sure that the harness is grounded to a clean metal surface. There cannot be any paint where the harness is grounded. Also, if you are using a factory grounding point that is already occupied by 1 or more items then I recommend moving the harness ground elsewhere.

Next you will want to test the wires going into the black converter box and the wires coming out. Use a circuit tester such as # PTW2993. Have someone sit in the cab of the vehicle and run through the lighting functions while testing the input wires with a circuit tester.

If there is no power, then that indicates a problem with the vehicle wiring that will need to be addressed. If it does show power move on to the output wires on the converter box. If there is no power coming out but there is power coming in AND the ground is sufficient then there is a problem inside the converter box, and it will need to be replaced.

I have included a couple of links that will help you troubleshoot.

expert reply by: Michael H