No Power On Trailer Wiring Harness Installed on a 2012 Jeep Liberty

Updated 04/18/2014 | Published 04/17/2014

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Question:

I have installed my t wire harness exactly as shown in the video provided. I have check all my grounds and power cord. I still cannot get my trailer lights to work at all. I even went as far as to buy new lights thinking its possible that the lights were the problem. Its a newly bought used trailer but the new lights wont work either. Everything is hooked up just exactly as shown in the video, all the way to the exact module location and and exact ground location. Is it possible that I just got a bad unit? Keep in mind Im not the most automotivly inclined. I just followed the video to the T.....

asked by: Justin

Expert Reply:

To determine if wiring harness # 118554 is the problem, you will want to test it. With the trailer disconnected you will need to use a circuit tester such as # PTW2993 to test the pins on the 4-Way end of the wiring harness while someone sits in the 2012 Liberty and runs through each light function.

If there is no power on the harness at the 4-Way then you can make sure that 1) the fuse is installed in the power wire, 2) the power wire is connected to the positive battery terminal, 3) the ground is attached to a clean and corrosion free bare metal surface that is not painted.

If everything is installed correctly and there is still no power to the 4-Way connector, then that does indicate a problem with the wiring harness, and it will need to be replaced. I have included some links that will help you troubleshoot.

If there is power on the 4-Way then the issue is on the trailer. It is likely a ground and/or wiring issue on the trailer. Make sure that the trailer connector is in good shape, no frayed wires or loose connections. You can trace the wiring from the front to the back to check it and fix as needed.

Make sure the main trailer connector ground and the grounds for all of the lights are attached to clean and corrosion free bare metal surfaces. Anything between the light ground and the trailer frame can interrupt the ground.

The same goes for aluminum frames, tilt beds, or folding tongues. You can run jumper wires from the light grounds to the main trailer connector ground to help if that is the issue.

expert reply by: Michael H