Running Lights on Trailer Not Working After Install Wiring Harness on a 2011 Nissan Frontier

Question:

Towing question. I have attached the trailer harness under the truck, I have signals and brake lights but no tail lights on the trailer. What could the cause be?

asked by: Tim S

Expert Reply:

There are a couple of things that could cause problem on the 2011 Nissan Frontier. First, if the truck did not come with the factory tow package then you will need the wiring harness that you have referenced # C56225. This harness comes with 3 relays that activate a 12 volt circuit and the turn signals. Sometimes there is an additional relay that you will need to get from a Nissan dealer that installs in the in-cab fuse panel.

If that additional relay is present then check the fuse that powers it (located right next to the relay). If that fuse is missing or blown then the running lights on the trailer will not work.

If everything is in the right place and no fuses are blown use a circuit tester like # PTW2979 to test the pins on the truck side trailer connector. If the running light signal is present at the connector then the issue is on the trailer, most likely a bad ground, so you will need to check the ground at each light and the main trailer connector ground. Also check the trailer side connector for dirt and corrosion.

If the running light signal is not coming through on truck side connector then there is a wiring problem somewhere on the truck and you will want to go back and check the installation and relays/fuses again according to the instructions I have linked for reference. I have also linked a video that should help.

expert reply by: Michael H