Troubleshooting Factory Trailer Wiring on 2012 Nissan Frontier

Question:

Okay, so when I originally hooked my 4-way trailer to the factory plug in at the back bumper, my trailer lights worked perfectly without a problem. Out of no where, I had no power. Immediately went to the 10amp fuse and replaced those with the fuses that light up so you can tell they work without the fuse test tool, supposedly - keep in mind, the replaced fuses weren’t blown, and once replaced, the fuses didn’t light up as described, at this time, the least of my problems, I thought. Then plugged the trailer into another truck’s 4-way receiver to find out it worked perfectly fine. After doing some reading, I checked under my kick panel to find out I didn’t have the relay kit part #c56225 , I believe that plugs into the 12-wire plug and has the 2 blue and 1 brown plugins on it, as well as replaced the 4-way pin that comes with it - just to eliminate that one at the same time. Now I’m running out of options as to what the problem can be, any ideas?

asked by: Gabriel P

Expert Reply:

Thanks for all the details of your troubleshooting efforts with the trailer wiring on your 2012 Frontier.

Since your old fuses were not blown and your new fuses that have the indicator lights did not light up this tends to suggest that your tow package relays are not working and this is why power is not making it to the fuses or to the trailer connector. On the passenger side of the engine compartment close to the windshield are both a fuse box and a smaller fuse/relay box. Both are shown in the linked diagram.

Check the smaller fuse/relay box to verify that the relays are installed. Since there is not an easy way to test a relay you can just try new ones to see if that activates the trailer wiring. We this relay in the Curt Relay Kit # C57000 or your local auto parts store will have replacement relays they can match up to yours. This should allow power to reach the fuses and for the trailer circuits to become active.

You can use a simple circuit tester like # PTW2992 to check the 4-pole circuits just in case it was a short on the trailer that caused the relays to fail. You can also test the trailer directly using the Frontier's battery or a spare if you have one. A set of jumper cables and two short lengths of wire make it easy to apply direct power to the trailer plug. Connect the battery negative terminal to the ground pin on the trailer 4-pole and then one by one apply the positive wire to each of the three circuits. The trailer lights should come on with this direct power input. If they do not then you know there is an issue on the trailer that needs to be corrected before you install new relays on the Frontier.

expert reply by: Adam R