With the available in-vehicle trailering app and the myGMC mobile app,1 you can activate the Trailer Light Sequence Test, which runs a lighting sequence of essential lights used in trailering. It only takes one person to conveniently activate this sequence and simply walk around the vehicle to inspect the lights.
1. Service availability, features and functionality are subject to limitations and vary by vehicle. App functionality and features vary with vehicle equipment and trim level, device and the plan you are enrolled in. myGMC Mobile app available on select Apple® and Android devices. Device data connection required. See onstar.com for more details.