The bumper cover on your 2006 GMC Sierra is held to the vehicle by a combination of bolts on the top of the bumper and on the support braces under the vehicle. Removing the bumper requires removing the front grille because it is attached to the bumper and prevents access to the upper mounting bolts. If the bumper is not being replaced and will be returned to the vehicle, have a safe place to put it while it is removed to prevent any damage.
Lift the vehicle hood. Remove the plastic pushpin retainers from the upper grille cover by prying the center pins up with a flat-tip screwdriver and pulling the pushpin assembly from the cover. There will be four that attach it to the grille and three that attach it to the core support. Remove the upper grille cover.
Turn the two plastic Phillips-head screw retainers in the upper corners of the grille one-quarter turn. Remove the bolt attaching the grille to the hood latch support with the socket and ratchet. Push in on the retainer clips at the fender and grille mating area with a flat-tip screwdriver while gently pulling on the ends of the grille to remove it from the vehicle.
Disconnect the wiring harness from both of the fog lamps if the truck is so equipped. Remove the bolts connecting the bumper to the support braces underneath the vehicle, using the socket and ratchet; this brace connection is about five inches from the bend at each end of the bumper.
Remove the four bolts at the top of the bumper -- two by each headlight -- with the socket and ratchet. Firmly grab the bumper and pull it straight off the truck, placing it on the blanket for protection if it is not being replaced.
Set the bumper onto the truck and hand-thread the four upper mounting bolts. Lie down under the vehicle and hand-tighten the two brace bolts. Tighten the upper mounting bolts to 63 foot-pounds of torque with the torque wrench. Tighten the brace bolts to 41 foot-pounds with the torque wrench.
Plug the wiring harness into the fog lights, if equipped.
Position the grille and push on the ends of the grille so that the retainers clip into their mounting holes on each fender. Turn the plastic Phillips-head retainers clockwise one-quarter turn.
Install the bolt connecting the grille to the hood latch support and tighten to 71 inch-pounds with the torque wrench.
Set the upper grille cover into place. Set each of the plastic retainers into their respective holes through the cover and into the grille and core support. Push in on the center pin until it sits flush with the base of the plastic pushpin retainer. Shut the vehicle hood.
