Troubleshooting Malfunctioning Trailer Connector on 2010 GMC Sierra 2500

Question:

I have a 2010 gmc sierra 2500hd and I have no trailer lights working at all. When checking voltage at connector I have main power but no power at any other poles when turn signals on, emergency lights on, etc

asked by: Terry N

Expert Reply:

As a first step, check the rear of the trailer connector where the trailer connector plugs into the factory harness. If this connection is not fully plugged in and the locking tab secured, it would explain why several of your trailer connector functions are not working. Plug the harness fully into the rear of the trailer connector and make sure the locking tab is engaged.

A less likely possibility would be some a blown fuses. The fuse box is located under the hood on the inside fender on the drivers side near the firewall. The underside of the lid or the owners manual should have a diagram showing which fuse protects which circuit. If you discover blown fuses, you can replace them, but before plugging a trailer back in, you will need to examine the trailer wiring to locate the short that caused the fuses to blow.

These two scenarios are the most likely reasons for the problem you are experiencing.

expert reply by: Mike L