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GMC Terrain Gas (2018–Present) Flat-4 Wiring Installation
Vehicle Coverage: 2018–Present GMC Terrain gas models with the compatible rear vehicle connector
Output: Exterior 4-way flat trailer-light connector
Connector Location: Mounted outside near the receiver
Connection: Plugs into the protected factory connector behind the center of the rear bumper
Body Wiring: No cutting or splicing of the factory lighting circuits
Connector Location: The completed flat-4 is mounted outside near the receiver and covered when not in use.
1. Isolating Vehicle Power
The negative battery terminal is isolated before the sealed rear connector is opened, protecting the lighting circuits during installation.
2. Accessing the Factory Rear Plug
The weather-sealed vehicle connector is located along the center rear bumper area. Its protective cap is released without damaging the locking tabs.
3. Installing the Exact-Fit Harness
The trailer harness is inserted fully into the factory connector and its lock is verified by hand. No factory lamp wires are cut, tapped, or spliced.
4. Routing and Mounting the Flat-4
The harness is supported along the hitch and secured away from exhaust heat, suspension movement, and sharp edges. The flat-4 is mounted near the receiver rather than left hanging below the bumper.
5. Testing and Weather Protection
Running lights, brake lights, both turn signals, and ground integrity are tested before the battery connection and lower area are finalized. A dust cover protects the exterior connector between uses.
Exterior, Exact-Fit Connection. The flat-4 is ready at the hitch without routing a cable through the Terrain’s hatch opening.