Troubleshooting Trailer Running Lights Not Functioning

Question:

COULD A BURNT HEADLIGHT ON THE TOW VEHICLE CAUSE TAIL LIGHTS NOT TO WORK ON A TRAILER BUT BLINKERS AND BRAKE LIGHTS WORK FINE?

asked by: JOE B

Expert Reply:

To give you the simple answer to this- No. Your headlight being burnt out won't have anything to do with trailer lights not functioning. It's more likely that there is an issue on the trailer wiring, in this case. I would recommend checking your 2017 Toyota Tundra's trailer connector to make sure that you're getting power on all of the pins; you'll need a circuit tester like the # PTW2993 to complete this. I would also make sure that you've got a good ground connection on the connector.

If everything on the vehicle side of the truck checks out, you'll want to check the trailer side wiring, behind the plug. It's likely that the running light circuit is the culprit here, so I'd pay special attention to the pin at 11 o'clock when looking at the vehicle plug receptacle. If you're getting power from the vehicle on that circuit, then the issue is likely on the trailer and you'll want to trace that wire back from the plug, checking for damage along the way. I also recommend checking the ground wire on the trailer to make sure it is firmly connected to the trailer frame.

If you can check this out and still haven't found the root of the issue, please let me know and I can help you further troubleshoot this. I've also linked some helpful articles on troubleshooting trailer wiring that I recommend taking a look at.

expert reply by: Erik B