2010 GMC Sierra 1500 Crew Cab Owner's Manual - Page 202

Object Detection Systems Ultrasonic Rear Parking Assist (URPA) For vehicles with the Ultrasonic Rear Parking Assist (URPA) system, it operates at speeds less than 8 km/h (5 mph), and assists the driver with parking and avoiding objects while in R (Reverse). The sensors on the rear bumper are used to detect the distance to an object up to 2.5 m (8 ft) behind the vehicle, and at least 25.4 cm (10 in) off the ground. { WARNING: The Ultrasonic Rear Parking Assist (URPA) system does not replace driver vision. It cannot detect: . Objects that are below the bumper, underneath the vehicle, or if they are too close or far from the vehicle Children, pedestrians, bicyclists, or pets. . If you do not use proper care before and while backing; vehicle damage, injury, or death could occur. Even with URPA, always check behind the vehicle before backing up. While backing, be sure to look for objects and check the vehicle's mirrors. 3-64