Troubleshooting Factory Trailer Wiring that has No Power

Expert Reply:

My first thought would be blown fuses, so I would be sure to double check all fuses and relays related to the tow package. This information will be listed in your owners manual. Check to ensure you are getting power at the trailer connector on your vehicle. Using a circuit tester like # 40376, test the vehicle side connector since it's factory trailer wiring.

Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. You could use a circuit tester to probe the wires on your truck moving toward the fuse box and see if you detect where the power terminates. If there is no power at all on the tow package wires and the fuses and relays are all good, you may want to take your truck a local dealer to inspect it.

If the wiring on your vehicle is okay, then the issue is on the trailer. The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

If your trailer has a lot of running lights, there could be too much power draw which could also lead to blown fuses. Switching to LED lights with much lower amperage would help in this situation.

Take a look at the help articles I included as well.