In 2002, Chevrolet unleashed a new model that was unlike most other utility vehicles. This all-new Avalanche was essentially an SUV up front and a pickup truck on the rear. This "sport utility truck" featured a double-decker front light setup where the turn signal assembly sat on top of the headlight assembly. This means that you must first remove the turn signal assembly before you can access the headlight bulbs. Chevrolet thought ahead and made removing this turn signal assembly a fairly simple task, leading to easier headlight replacement on your 2003 Avalanche.
Look on the rear of the turn signal assembly and find the locking tab on the outer edge of the assembly. Press the locking tab to release the turn signal assembly, then pull the outer edge of the turn signal assembly away from the body until it clears the fender. Pull the turn signal assembly from the Avalanche and set it aside.
Find the two L-shaped retaining pins securing the rear of the headlight assembly to the vehicle. Pull the top of each L-shaped pin away from its locking clasp to unlock it, then pull the pins upward to remove them from the vehicle. Pull the headlight assembly from the front of the Avalanche just enough to access the bulbs on its backside.
Rotate the headlight bulb counterclockwise to unlock it and pull it from the headlight assembly. Lift the locking tab on the wiring harness to unlock it and pull the bulb from the socket.
Hold a new headlight bulb -- No. 9006 for the low beam or No. 9011 for the high beam -- by its plastic base. Avoid touching the glass part of the bulb with your bare hands, as the oils from your hands can cause premature bulb failure. Plug the wiring harness into the new bulb, then install the new bulb and socket into the headlight. Rotate the new bulb clockwise to lock it in place.
Guide the headlight assembly into its bed on the front of the truck, so the locating holes -- the holes that the L-shaped pins feed through -- line up with the locating holes on the front of the truck. Insert the L-shaped pins into the locating holes to secure the headlight assembly, then rotate the pins to latch them into their respective locking clasps.
Insert the tab on the inner edge of the turn signal assembly into the slot just behind the grille and press the outer edge of the turn signal assembly toward the front of the truck until its locking tab clicks into place.
