Trailer Turn Signals Not Working After Installing Trailer Wiring Harness on 2008 Kia Sorento

Question:

i have a 2008 sorento and hooked up a trailor. i have no turn signals on trailer. Have checked all fuses

asked by: Susan J

Expert Reply:

The Curtwiring harness # C56332 is designed to fit a 2008 Kia Sorento that came with the factory tow package. You can have the dealer run the VIN to determine if your Sorento was equipped with a factory tow package. If it was not then you would need to use a hard wire harness, # C59496.

If it does have the factory tow package then there is most likely a bad ground causing the problem or, if the vehicle uses relays for its tow package wiring, a bad relay. Relays can be obtained from a Kia dealer. If the brake lights work and it is just the turn signals that do not then it is more likely a ground because on a trailer, the brake lights and turn signals are on the same circuit on each side.

We need to isolate where the problem is. First disconnect the trailer and use a circuit tester, # PTW2993 if you need one, to test the trailer wiring harness on the vehicle. First test the wires that go into the converter box. On harness # C56332, these are the wires covered up by the loom.

If the signals going in are not correct then there is something wrong on the vehicle side; a missing relay, fuse, or a bent or broken pin where the harness connects to the vehicle. If the signals are correct going into the box, the next step is to test the 4-Way end.

If the signals are not correct at the 4-Way, then there is something wrong with the converter and the wiring harness will need to be replaced. If everything is correct on the vehicle, then that indicates a problem on the trailer.

On the trailer side make sure the connector is clean and free of corrosion. Make sure the main trailer connector ground and all the grounds for the lights are attached to clean and corrosion free bare metal surfaces. You can use the same circuit tester to make sure the power is getting back to the lights. If it is not, then there is a break somewhere in the wiring between the connector and the lights.

If the trailer has an aluminum frame, tilt bed, or folding tongue, or if you recently added a plastic license plate holder between a tail light ground and the trailer frame, any of those things can interrupt the ground connection. Running jumper grounds from the lights to the main trailer connector ground can help fix this.

I have included a link to an FAQ article that will help you troubleshoot.