Troubleshooting Right Side Trailer Running Lights Not Working

Question:

Hi - I have a 2004 Toyota 4Runner Limited that I use to tow my small boat. Last year I replaced the old trailer lights with LED lights. Everything has been working perfectly until the other day. Just prior to leaving the driveway for a short trip to the lake, I noticed that the right-side trailer tail light was not working. The turn signal functions well, as does the brake light. I cleaned and re-secured a couple of ground wires to no avail. From what I can gather, the brown wire on the LED harness is for tail lights I visually inspected the brown wire at both ends and found nothing. Can you advise, please? Thanks.

asked by: Alan L

Helpful Expert Reply:

The trailer running lights use a single dedicated circuit from the connector on your 4Runner so if just the right side running lights aren't working then we know the problem is somewhere on the trailer, and not the tow vehicle.

The fact that only the right side on the trailer isn't working actually helps to narrow down the potential cause quite a bit, as the fault could really only be with the tail light itself (which works fine for the brake/turn so we can rule that out) or with the tail light wire that runs along the right side of the trailer.

Since you already checked and re-secured your grounds your best next step is to just try and trace this brown wire its entire length down the right side, looking for any pinched, exposed, or damaged sections that need to be replaced. I know this might be difficult to do depending on how hidden the wiring is so if it's just not possible you can also just cut the wire at both ends and run a new one with some 16 gauge wire like # 16-1-1 (sold by the foot).

If this does not resolve the issue please let me know and we can continue to troubleshoot.

expert reply by: Chris R