Trailer Brake Lights Not Working when Connected to a 2003 Toyota Tacoma

Updated 04/13/2015 | Published 04/10/2015

Question:

i2003 toyota tacoma brake lights work turn signals on truck work plug into trailer and i have running light turn signals but no brake lights is it the convertor box under seat ?

asked by: Dave

Expert Reply:

Does your 2003 Toyota Tacoma have a factory tow package and trailer connector? If so then it could be a blown fuse associated with the tow package wiring. Many times, the tow package wiring is separate from the vehicle tail light wiring so the truck brake lights working would make sense.

If it is an aftermarket wiring harness such as # 118379 then it is strange that the brake lights on the trailer are not working because the brake lights and turn signals are on the same circuit.

This makes me think that there is a bad ground connection. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light.

Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces.

The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

expert reply by: Michael H