Troubleshooting A Disconnected Wiring Harness and 7-Way Connector On 2018 Chevrolet Silverado 2500

Updated 06/11/2022 | Published 06/10/2022

Question:

My after market plug for my trailer wire harness pulled apart. A buddy of mine installed it so not sure where the wires go back to. Its a 7 prong plug but only 7 wires. Black yellow green white and 2 browns. And there is no spot on connector that says for a yellow wire.

asked by: Jesse L

Expert Reply:

Your 2018 Chevrolet Silverado has a factory plug underneath the vehicle at the rear on the driver's side. If you have an aftermarket 7-way connector, it plugged into the factory harness underneath your vehicle. The first thing I would do is check to see if these plugs are connected. If not, you should be able to reconnect these plugs and get your 7-way functionality back. The prongs on a 7-way connector have specific functions. The wires are color coded and there is one for each prong. They are usually as follows:

Green for tail/running lights
Black for 12V hot lead
Yellow for reverse lights
Brown for taillights/running lights
Red for 12 V hot lead
Blue for brake controller
White for the ground

The yellow wire may be for your reverse lights or your left turn signal. In your case I believe you may have two browns for both turn/stop signals. It appears you are missing the blue wire for a brake controller. If you have a trailer that weighs less than 3,000 lbs, you might not be required to have trailer brakes.

If you did lose a wire during when these plugs pulled apart, you can replace it with the Reese Multi-Plug Wiring Harness for Factory Tow Package - 7-Way and 4-Way Flat Trailer Connectors, part # 74682. I have included a video of this wiring harness being installed on a 2017 Chevrolet Silverado 1500 below. You can also use this video to find the wiring harness under your vehicle.