Troubleshooting Trailer Tail Lights not Working when Tow Vehicle Head Lights are On, Toyota Tundra

Question:

All started when I switched vehicles. Had GMC Seirra. Now have Toyota Tundra. All worked fine before. With head lights off trailer lights work as they should. When head lights on I have no trailer flasher or hazards. The trailer brake lights stay on all the time. Any ideas?

asked by: Don L

Expert Reply:

This to me sounds like a ground problem. It sounds like your tail lights function until the additional load of having the head lights of your vehicle are turned on and then the lights cut out.

The reason this manifested after the vehicle swap could be a lower voltage output of your latest vehicle. Either way I would check the grounds on the tail lights of your vehicle and make sure they are making a good connection to a clean metal surface.

I attached an FAQ on trailer wiring for you to check out also.

expert reply by: Jameson C