Vehicle Taillights Shut Off with Trailer Plugged Into a 2012 GMC Terrain

Updated 07/15/2019 | Published 07/13/2019

Question:

I recently had a tow hitch and 7 pin plug installed on my 2012 GMC Terrain. When I plug my camper into the 7 pin receiver and turn the lights on the camper lights come on for 1 second and go out. The left rear tail light on the Terrain also goes out. The rest of the lights on the Terrain stay on. When I unplug the camper the left rear tail light stays out. When I turn the lights off and shut the Terrain off and restart the Terrain and turn the lights on, the left rear tail light comes back on. Everything on the camper and Terrain works except for the tail light and camper marker lights. When I plug my camper into my 2014 F-150 everything works on both. Any idea why only the left rear tail light and the camper marker lights go out when plugged into the Terrain?

asked by: Matt M

Expert Reply:

There could be a few different issues with your setup but since you have towed the trailer with your other tow vehicle and there were no issues then that means the issue is with your 2012 GMC Terrain. I did not catch what trailer wiring harness that you were using but the first thing I would check is the ground for this harness. This is most likely the cause but if the vehicle's taillights are also cutting out then that leads me to believe you could be overloading the circuit. If you are towing a trailer with a bunch of lights then this may be too much for the lighting circuit on your Terrain to handle therefore a trailer wiring harness with a powered converter, the T-One Vehicle Wiring Harness part # 118494 is what I recommend.

expert reply by: Conner L