Troubleshooting Trailer Wiring Harness on a 2004 Toyota Tacoma

Updated 07/03/2017 | Published 07/01/2017

Question:

Installed your part # 118379 on my 2004 Toyota Tacoma. When I turn on the running lights the brake or signal light wont work on the trailer. With the running lights off signal and brake lights work fine. Many-thanks

asked by: Dennis V

Expert Reply:

The issue you're having is almost always caused by a week ground. It's strong enough to handle the power draw of the running lights or the turn and brake signals but not both at the same time. I would start be reconnecting your grounds to clean bare metal connections. Or if the trailer lights are grounded through the mounting hardware make sure the studs are clean and free of any corrosion.

If this doesn't solve your issue you'll need to inspect the wiring. If you still can't find the problem let me know what you have tested and found and we'll keep troubleshooting.

expert reply by: Charles S