Trailer Lights Function Differently on Two Different Vehicles

Question:

I have a small trailer with 4 pin flat. I also have a 2013 Ford - 150 and a 2015 Lexus GX460. When my trailer is plugged into the f-150 everything works except the running lights both side marker and rear. When plugged into my Lexus ONLY the side marker running lights work. Also, I used a self tapper and grounded each of the lights to the frame and then ran the white wire to tongue via self tapping screw.

asked by: Dustin H

Expert Reply:

If you have different lighting issues with the trailer depending on which vehicle you are using then that leads me to believe there is an issue on the vehicle. I recommend you check the trailer lighting circuit fuses on each tow vehicle to make sure all is in order. Also, I recommend you run a ground jumper wire for each light up to the main trailer connector ground as well temporarily to see if that fixes your issue. If you want to check the trailer on its own then you can do so with the battery in either vehicle by just applying a hot lead to each of the circuits.

I have attached for you below some trailer wiring help articles you will want to take a look at.

expert reply by: Conner L