Trailer Brake Lights/Turn Signals Not Working After Installing Wiring Harness on 2006 Toyota Sienna

Question:

Hi, I installed trailer wiring harness on 2006 sienna however all I have working is running lights - brake and turn signals are not working on trailer. Any idea how I can fix this?

asked by: Drew

Expert Reply:

To determine if the issue is on the trailer or the 2006 Toyota Sienna you will first disconnect the trailer from the van. Then use a circuit tester such as # PTW2993 to test the vehicle side wiring. First test the wires going into the converter box on harness # 118304 from the vehicle. Have someone sit in the cab and run through the light functions while testing the wires.

If there is no power on the input wires for brake lights or turn signals, then there is something wrong with the vehicle wiring that will need to be addressed and fixed. But if there is power when there is supposed to be you can move on to the next step.

The next step is to test the wires coming out of the converter that go to the 4-Way trailer connector. If there is power when there is supposed to be on the output side, then the issue is on the trailer. But if there isn't power when there is supposed to be that indicates a problem with the converter and it will have to be replaced.

If everything on the vehicle side is working, then the issue is on the trailer. make sure the trailer connector is clean and free of corrosion. Make sure the main trailer connector ground and grounds to all of the lights are attached to clean and corrosion-free bare metal surfaces.

If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

expert reply by: Michael H