Troubleshooting Left Side Trailer Running Lights that are Not Working

Published 10/13/2016

Products Featured in This Question

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

(414)

$28.83

Hook Probe Circuit Tester

(61)

$13.33

Question:

I have installed the harness according to the instructions and grounded the white wire to the sheet metal. but the driver side tail light and side maker of the vehicle will not go on the brake light and turn indicator work, but running lights will not nor will the trailer running light go on, whats wrong??? please help

asked by: John B

Expert Reply:

The first thing you'll want to do is determine if the problem is with the new wiring harness on your 2008 Buick Enclave or on your trailer. Both sides of the tail and marker lights run on the brown wire. Since you have only one side working the problem is most likely with the trailer.

Use a circuit tester, like PTW2993, and test each contact on the new 4-pole connector. If they all pass, then check the wiring on your trailer. I would start by inspecting the trailer's connector, making sure it's clean and corrosion free. Then check the ground wires on the driver's side. Make sure they're connected to a smooth, clean surface like you did when you installed the harness on your Buick. If there's no issue with the ground, you'll want to inspect the wiring going to the lights that are not working and look for any kinks or pinches along the way. If you find any then you'll want to repair it.

If after you've gone through these steps and you're still having an issue, let me know and we'll look into some more troubleshooting steps.

expert reply by: Charles S