Troubleshooting Running Lights on Trailer Not Working With Curt # C56217 on 2018 Toyota Highlander

Updated 06/11/2021 | Published 06/09/2021

Products Featured in This Question

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

(1097)

$40.86

LCD Digital Circuit Tester

(24)

$27.59

Question:

Installed and turn and brake lights work but regular headlights on , tail lights don’t light

asked by: Chris T

Expert Reply:

First you will need to determine if the lighting issue is in the vehicle side of the wiring or the trailer. A Test Light # PTW2992 will help you to test the 4-way plug. Simply connect the clamp side of the test light to either the ground lug of the 4-way for to a good chassis ground. You can then activate the headlights on your 2018 Toyota Highlander to check for power to the brown wire connector. This is the one closest to the ground terminal on the 4-way.

If you have power here the problem is in the trailer wiring. You can continue to use the test light to follow the wiring to the lights looking for a break in the wiring or where it may have shorted to ground. I have linked an article below that will cover the trailer wiring.

If you do not have power at the 4-way you will want to inspect the connectors on the wiring harness to determine if there may be a damaged pin or a wire has come out of the connector. I have linked a video below for reference as well.

Lastly check to ensure that the fuse for the wiring is still good and that there are no damaged fuses in the vehicle circuit for the running lights.

expert reply by: Bud M