Troubleshooting Passenger Side Trailer Lights Not Working Until Trailer Is Hitched To Truck

Updated 07/06/2021 | Published 07/03/2021

Question:

Passenger side of trailer lights doesnt work. Put trailer on my pickup they work??

asked by: Fredrick

Expert Reply:

Based on your description it sounds like if the trailer is not hitched to the truck but the wiring harness is plugged in the passenger side trailer tail lights do not work, but if the trailer is hitch to the truck that the lights starting working.

If this is the case then there is a ground issue on either the truck or trailer. I recommend starting with the main trailer ground on the tongue of the trailer making sure it is securely connected to clean corrosion free metal.

If those grounds like good then check the ground for the trailer connector on your truck. If it is an aftermarket harness make sure the ground wire with the ring terminal is secured to the frame in a location that is clean and corrosion free.

I included a link to a helpful article on wiring for you to take a look at.

expert reply by: Samuel C