Troubleshooting 4-Way Vehicle Wiring Harness Not Allowing Brake Lights to Work on 2003 Toyota Tacoma

Published 03/25/2024

Products Featured in This Question

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

(218)

$59.64

Curt Powered Tail Light Converter with 4-Pole Flat Trailer Connector

(1817)

$80.47

Question:

Hello Etrailer team, I have used your wiring harness installation kit from Curt for my 2003 tacoma double cab. I am at the final stage of connecting the harness and grounding it. Everything is working properly, but my brake lights. It appears that they are now always on, or maybe they are just at tail light brightness. Either way pressing and depressing the pedal makes no difference in the brightness of the taillights. The tail lights are aftermarket LED. Could this be having an impact on the harness or is this likely being caused by something else?

asked by: Chris B

Expert Reply:

The 4-Way Harness # C55379 for your 2003 Toyota Tacoma is going to use the factory wiring to identify when a function is activated and power the trailer connector. Since you mentioned your truck was converted to LED lights if you factory lighting has a resistor installed going to the brake lights this may prevent enough power from getting to the tail lights. You may have to either move the resistor or go with a powered module like the # C59236. This has a separate power wire which runs to the battery so that all the power sent through the converter is coming from the battery rather than the factory wiring.

I would start by testing the input wire going into the converter you just installed to verify you are getting power from the brake switch. I have also seen the fuse for the brake lights go out because the battery wasn't disconnected and there was a power short during installation. Since both the brake lights aren't working I feel like this is the most probable issue. Please let me know what you find or other tests you may have done so I know where to go further to help you determine it the converter was bad from the factory.

expert reply by: Bud M