Brake Light & Turn Signal Will Not Work on One Side of a Trailer Connected to 2008 Toyota FJ Cruiser
Updated 04/25/2018 | Published 04/24/2018
Question:
I have replaced the wiring harness from the 4-Pole connector factory wiring plug to the 4-pole connector that my trailer wiring harness connects to came with the rear lamp kit, wiring back to the trailer lights, new set of trailer lights, and I still cannot get the right side drivers side -left turn signal to blink, emergency blink or brake light. I have running lights on both passenger side and drivers side. I have even purchased a second drivers side lamp t make sure that I did not burn the bulb out while testing. Is it possible that there is a fuse for the this drivers side blinker lamp that has burned out? My guesses are over, and I hate to take it into a garage to re-wired for me, but I am out of whys?
asked by: Keith W
Expert Reply:
The easiest way to determine if the problem is on the vehicle side or the trailer side is to do a little testing. First, with the trailer disconnected, have someone sit in the tow vehicle to operate the lighting functions. Then use a circuit tester such as # PTW2993 to test the connector on the tow vehicle. If the connector does not show any power when it is supposed to then the issue is on the vehicle. If it does work as it should, then the issue is on the trailer.
On the vehicle side it very well could be fuse related. There are a couple of fuses for the factory tow package under the hood of the 2008 Toyota FJ Cruiser but neither of those is specifically for the trailer turn signals or brake lights. There does not appear to be a tow package fuse in the cab fuse box either.
There could be an issue with the factory wiring harness that the 4-Way plugs into. You can perform the same test as above on it to see if it is the problem. If so then a Toyota dealer would have to replace that. Or you could bypass the factory wiring altogether and use # 118405 which plugs in line with the vehicle tail light wiring.
If everything on the vehicle side checks out, then the issue is on the trailer. Trailers that have a ground problem will sometimes work fine when the trailer is coupled to the ball. But trailer lights are not supposed to ground this way so if that is the only time it works then that does indicate a ground problem.
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 but can show up any time.
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.
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