Troubleshooting No Left Side Trailer lighting on a 2005 Nissan Titan with Factory 7 and 4-Way Wiring

Expert Reply:

You do not need to have an additional 4-Way wiring harness, # 118384, for proper operation of the trailer lights when you have a factory 7 and 4-Way connector. I would start out by checking the trailer connectors at the rear of the vehicle with a circuit tester, # 3808, no trailer attached. This will let you know if the problem is on the vehicle side or trailer side.

If you find the problem is on the vehicle side, check the relays that are under the hood of your 2005 Nissan Titan to be sure that they are there, installed and working correctly. We have a wiring video installation that shows where the relays should be installed at about the 6 minute mark of the video. You should have two blue relays that activate the left and right turn signal functions. If one is not present you will need one. These relays can be purchased in the Curt Relay Kit for Nissan, # C57000, or at the vehicle dealer.

If both relays are installed, the left side relay may be bad. I would try removing the left side relay and installing the right side relay in that location to see if that does not solve the issue.

If you find that the relays are not the problem, you will need to turn your attention to the trailer connectors and wiring at the back of the truck, check for corrosion or bad wires that could be causing the issue. If a new connector is needed you could use the 7-Way and 4-Way trailer connector, # N40975, to replace the truck connector.

If you find that the issue is with the trailer wiring, you will need to test the trailer wiring and connector to run down the problem. We have a trailer wiring page, see link, that should be helpful when testing the trailer wiring. Make sure the ground wires and trailer lights are securely grounded to paint and rust free parts of the trailer frame and that there is no corrosion in the connector causing the issue.

expert reply by: Bob G