GMC Terrain OE Wiring Harnesses & Stereo Adapters - CARiD We have you covered with top-notch wiring harnesses designed precisely for your GMC Terrain by the most trustworthy brands in the industry. GMC Terrain wire harnesses showcased on our digital shelves provide efficient, worry-free operation of many parts of the vehicle. Also, it makes installation a breeze. GMC Wiring Harnesses - Car Audio Stereo - Car Subwoofers Are you in the process of replacing your GMC factory radio with an after-market car stereo? Avoid having to cut OE plugs and making a mess of it all! Our GMC wiring harnesses can help you perform a clean installation without hassle.