Troubleshooting Check Trailer Wiring Message on 2021 GMC Denali Sierra 2500 After Driving

Question:

2021 gmc Denali 3qtr ton 4x4 I plug in the trailer harness the vehicle recognized the trailer but after a few feet of travel the warning message check trailer wiring

asked by: Randy

Expert Reply:

Seeing as your 2021 GMC Sierra 2500 Denali recognizes the trailer but then shows the error message once you start driving leads me to believe the issue is with your trailer. I would start by checking the 7-way connector and adding Dielectric Grease # 11755 to the connector. If the issue still continues you will likely either have a bad ground on the trailer or short in the wiring. I have linked one of our help articles below which goes in depth on 7-way wiring which will help you further understand where the wiring goes. You will want to start checking for physical damage to the wiring and inspecting the junction box.

expert reply by: Bud M