Chevrolet 2003 Silverado 1500 Pickup Owner's Manual page 303

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.
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