Troubleshooting Turn Signal and Brake Lamp Circuit in Trailer Taillight Wiring  

Question:

Expert Reply:

The first thing you'll want to check is the trailer connector on the vehicle. You can use a circuit tester like # PTW2993 on the pins for the right/left turn as a helper activates them.

If you're getting signal for right/left turn and the brake lamps on the pins of the 4-pole trailer connector fed by the yellow and the green wires, then the problem exists in the trailer wiring.

If you're not getting signal on those pins, be sure that the taillight converter harness has been plugged in fully. Use the circuit tester to check the yellow and green wires on the input side of the converter box as the turn signals are activated. If you have signal entering, but not leaving the box, the converter has been shorted out and should be replaced. You'll need to locate the short in the trailer wiring and repair it before plugging the trailer back in, or you'll continue to short out the converter/harness.

If the connector on the vehicle checks out okay, examine the trailer connector on the trailer. Make sure the connector itself isn't damaged or corroded and replace or repair as needed. Trace the wiring from the connector back to the lamps, checking for loose connections, nicked wires or wires with worn or cracked insulation. Repair as needed.

I'll link to a help article that will help further troubleshoot your trailer wiring.

expert reply by: Mike L

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