Troubleshooting Trailer Wiring when 2015 GMC Sierra DIC Message Says To Check Trailer Wiring

Question:

The message comes on intermitantly with trailer connected.Will this test the factory controller and wiring on 2015 GMC truck? What conditions make message come on? Does the message even pertain to the brake controller or perhaps the signal given from the controller for the brake lights?

asked by: Greg

Helpful Expert Reply:

Based on my research and information from the 2015 GMC Sierra 2500's owner's manual, the "check trailer wiring" message means that either a trailer with electric brakes has disconnected from the Sierra, or there is a short in the wiring to the trailer's electric brakes. The owner's manual says that when this message appears, it means there is not longer power running to the trailer brakes.

You will want to check the wiring on both the vehicle and trailer that leads to the trailer's electric brakes for any pinches, tears, or other damage.

Since your vehicle is new, it is likely that the trailer is what is causing the issue. You will want to thoroughly inspect the wire running from the trailer connector back to each of the brakes. If there is any damage to the wire, you will want to replace the wire with new wire, like # 10-1-1.

You will also want to check the trailer connector and make sure if is free of corrosion. If the connector is corroded, it will not make a good connection with the vehicle connector. If the trailer's connector has corroded, you will want to repair or replace the connector. If you need a replacement connector, you could use a pre-wired connector like # H20046.

If neither the connector or the wiring is the problem, your brake magnets may need to be replaced. If you can see windings in the brake magnet, the magnet will need to be replaced. I have attached a help article on how to test trailer brake magnets for you. If you need to replace your trailer brakes or brake magnets, let me know the size of your brakes and the weight capacity of your axle and I will be glad to help you.

expert reply by: Victoria B