Troubleshooting 2008 Toyota Sienna With Trailer Running Lights Not Working

Updated 04/26/2017 | Published 04/25/2017

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

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$45.44

Hook Probe Circuit Tester

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Question:

My boat trailer had a short in the wiring which caused a fuse to blow in my pick up truck and also in my 2008 Toyota Sienna. When I tow the trailer with my Toyota the turn signals and brake lights work but the tail lights on the trailer do not. Is there a fuse that can be replaced within the wiring harness itself? There is not a separate fuse for trailer lights according to the owners manual in the Toyota like there is on my truck so I dont know which fuse would have blow in the Toyota. Any insight?

asked by: Marc S

Expert Reply:

There is not a separate fuse in the wiring harness itself. Normally for the functions like stop and turn to work but the running lights not to work is a bad ground wire connection on the vehicle or the trailer. Running lights stay on, so they draw more current than the other functions. Check the wiring harnes ground wire (normally white) where it attaches to the vehicle and make sure you have a clean metal to metal connection. Also check the trailer ground for the same. Any corrosion, rust, or paint could cause this issue, so clean it up and make sure there is solid metal to metal contact.

If you lights still don't work after that, use a tester like # PTW2993 to check the functions on your vehicle at the plug. If the running lights don't function there, I recommend replacing your wiring harness.

expert reply by: Jason S