Troubleshooting Trailer Running Lights Not Working with 2018 Nissan Frontier

Updated 01/19/2026 | Published 07/23/2019

Question:

I need a blue relay. the installation video calls for tow harness to be hooked up at passenger side kick panel, then 3 relays to plug to nearness, other instructions mentioned relay plugs under steering column? My issue is: trailer running lights dont work, brake/signals do.

asked by: Juan M

Expert Reply:

On certain Nissan vehicles like yours a 4th blue relay is sometimes needed to activate the trailer running lights circuit. This appears to be the case with your 2018 Nissan Frontier.

The blue relay that you need is included in the Curt Relay Kit # C57000 and the harness you need to access to plug the relay in is indeed located in the cab behind the dash to the left of the steering column. I have attached an image that might help.

expert reply by: Chris R

click to enlarge

Cito

1/19/2026

From looking at the picture, and seeing other posts, don't you mean RIGHT by passenger seat near glove box? Just curious as this has become a witch hunt and I am excited to see this post.