Your 2004 Chevy Impala uses bulbs for headlights, parking lights, turn signals and backup lights. The main differences among bulbs are the wattage, the size and the socket.
Headlight high beams use bulb number 9005, and low beams use 9006. Front turn signal lights use bulb number 3357NAK or 3457NAK.
Brake lights and tail lights use bulb number 3057. Your backup lights use bulb number 921.
Your Impala owner's manual has a bulb replacement chart on page 5-56. An online copy of the owner's manual is available at the Auto Manuals Online website. To download the manual, you must retype a pass code and check a box stating you are not driving while downloading. There is no direct link.
