Troubleshooting Trailer Running Lights Not Working on Toyota Pickup  

Question:

Helpful Expert Reply:

The T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118379 is a confirmed fit for your 1992 Toyota pickup. With the turn signals working and emergency lights working but the running lights not working, the issue most likely is in the ground wire of your trailer.

Here is how to troubleshoot. Use a circuit tester like # PTW2993 to check the pin function on each of the 3 power pins on your 4-way when the trailer is not connected. The running lights will be the brown wire that is next to the metal pin for ground. If the running lights don't work at the vehicle side connection, then check your owners manual for a fuse issue.

If everything works at the vehicle side, then first check your ground wire on your trailer where it connects to the trailer frame. Make sure this connection is bare metal to metal and free of corrosion, rust, and debris. When a single function doesn't work, a ground connection is often at fault even if it looks like a good connection. Then check the fixtures to ensure there isn't a separate bulb for the running lights that has blown. Next, use a little sand paper on the connection terminals to ensure you get a good connection between your vehicle and trailer. Finally, use the circuit tester to trace the running light wire probing thru the insulation every few feet to find a short. Replace as needed with # 16-1-1. I've attached a wiring article to assist.

expert reply by: Jason S

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