Trailer Lights have Stopped Working on a 2004 Nissan Titan with Factory Tow Package

Updated 09/20/2011 | Published 09/19/2011

Question:

I have a factory installed wiring harness, 7 pin, and use a 7 to 4 Plug Convertor for the small trailer. All lights had been working fine, but now only the Left Turn Signal works on any trailer. The Brake Light, Right Turn and Running Lights do not work, I measured for voltage at Connector itself. I can read full 12 Volts at the Pos. and Neg. pins on the 7 pin connector as normal. Have checked and found no fuses blown. Out of ideas? Thanks.

asked by: John D

Expert Reply:

This sounds like a ground problem. What you can do is start by check the trailer side and vehicle side trailer connectors. You will want to look for any dirt or corrosion in or behind the trailer connectors. Corrosion can cause any number of lighting issues.

Next move on to checking the ground connections for each connector to see that they are attached to clean and corrosion free bare metal surfaces.

You can then check the tail lights themselves. Again you are looking to see that the grounds are attached to clean metal surfaces. If all of the grounds check out, there could be a problem with the power wiring to the trailer lights.

You will want to check the wiring from the connector back to the tail lights looking for breaks or nicks in the wiring. You can also use a circuit tester like the one you have to test the wiring periodically to determine if there is a break you cannot see.

It is also possible that the relays on the vehicle need to be replaced. You could use Replacement Relays, # C57000, if you find that one or both relays (2004 Nissan Titan trucks only use 2 relays) are bad. Use the owners manual to find the location of the relays.

expert reply by: Michael H