2004 GMC Sierra 1500 Pickup Owner's Manual - Page 317

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. The following steps must be performed on each of the push-pins to remove the air dam: 1. Insert a tool into the push-pin slot and pull downward until the push-pin snaps loose. 2. While continuing to pull downward on the push-pin, squeeze and turn the expandable end of the push-pin with a tool until it releases from the retainer. 3. Pull the push-pins and lower dam assembly away from the retainers until the lower dam is free. 4-21