Trailer Turn Signals Not Working with Curt Trailer Wiring Harness on 2000 Toyota Sienna

Updated 07/13/2015 | Published 07/10/2015

Question:

I installed the CURT kit and the brake and headlights work on the trailer. No turn signals though. All work fine with another vehicle. What could be causing a subset of the circuit not to work? Its plug and play with the connectors so it seems as though if connected to one they should be connected to all. Thanks for your help!

asked by: Danny

Expert Reply:

The turn signals and brake lights are on the same circuits, but the running lights are on a separate circuit. The brake lights working but not the turn signals are strange since they are on the same circuit. You will need to test the wiring harness to determine if the problem is in the converter or elsewhere.

Basically, you will use a circuit tester such as # PTW2993 to test the wires going into and coming out of the converter box. First test the wires going into the converter. If everything shows power when it should then move on to testing the output wires. But if the turn signals are not showing power on the input side of the converter that would indicate and issue on the vehicle wiring.

You will perform the same test on the output side. If there is no power on the yellow or green wires when there should be (with the turn signals on) then there is something wrong with the converter and the wiring harness will need to be replaced.

Also, make sure that the harness ground wire is attached to a clean and corrosion free bare metal surface. Make sure the trailer connectors are clean and free of corrosion. The light grounds should also be 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