Troubleshooting Trailer Lights Not Working on a Trailer Towed by a 2000 Nissan Frontier

Question:

I installed my wiring harness as per instructions. All truck lights work but no trailer lights. Can the harness be bad? I have a 2000 Nissan Frontier Crew Cab.

asked by: Tristan B

Expert Reply:

You can test to see if the T-One Vehicle Wiring Harness, # 118362, is bad. First, with no trailer connected, use a circuit tester like # PTW2993 to test the pins on the 4-Way. If they do not work when you run through the lighting functions, then there is a problem on the truck side.

You can also check to make sure that all fuses/relays related to trailer towing are intact. Use your vehicle owner's manual to find the location of those fuses or relays.

Make sure that the white ground wire on the harness is connected to a clean and corrosion free bare metal surface. If it is not, it will need to be in order for the wiring harness to work. Next, test the wiring going into the converter box for proper function. If it is correct going in but not coming out, then there is a problem with the converter and the harness will need to be replaced.

If the signals are not correct going in then it may be connected wrong, but this is unlikely as there is really only one way those plugs can attach. If we rule out the truck, then the only thing left is the trailer. Make sure that both vehicle and trailer side connectors are clean and corrosion free. Next, check the grounds on the trailer.

The main ground on the trailer should be attached to a clean and corrosion free bare metal surface. The same goes for the trailer tail lights that normally ground through the mounting studs. If everything checks out, you can trace each of the wires, and look for any breaks, cuts, frayed wires, or loose connections.

expert reply by: Michael H