2001 GMC Yukon Owner's Manual - Page 220

The following steps must be performed on each of the push-pins to remove the air dam: 1. Insert the blade portion of a flat-tip screwdriver into the push-pin slot and pull downward until the push-pin snaps loose. The front bumper lower air dam is held in place by a series of push pins located around the lower edge of the front bumper. The push-pins are accessible from underneath the front bumper. 2. While continuing to pull downward on the push-pin, squeeze and turn the expandable end of the push-pin with a pair of pliers until it releases from the retainer. 4-17