The high-mount stoplight or combination light assembly, as Hyundai calls it, on the rear of the 2007 Sonata uses a #921 bulb, which is a key part of the Sonata's rear lighting system. The light is designed to be highly visible to drivers behind you when the Sonata's brakes are applied and helps to avoid rear-end collisions. Removal of the Sonata's taillight assembly is required to replace the stoplight.
Open the trunk of your Sonata and lay on your back inside the trunk looking up at the bottom of the package tray, or rear deck, directly below where the light assembly sits. Locate the two gold-colored Phillips head screws that retain the light assembly.
Remove the two retaining screws using a long Phillips screwdriver then move to the inside of the car to access the light assembly on the top side of the rear deck, which is inside the passenger compartment. Lift the rear of the assembly slightly while pulling it forward to free it from the package tray. Turn the assembly over and locate the bulb socket on the underside.
Rotate the bulb socket counterclockwise to unlock it, then pull it out of the taillight housing. Grasp the bulb, pull it straight out of the socket and discard it. Push a new #921 bulb into the socket; make sure it seats completely.
Slide the bulb and socket into the taillight assembly then rotate the socket clockwise a quarter turn, locking it in place. Turn the taillight assembly over, slide the tabs on the bottom of the assembly in the holes in the package tray and slide the assembly forward until it sits flat on the tray.
Move to the trunk and reinstall the two Phillips head screws with the long screwdriver. Tighten the screws until they are snug. Do not over-tighten these screws or you will crack the taillight assembly.
Close the trunk and test the light; have someone step on the brake pedal or watch the light while you press the pedal. If the light functions properly, the repair is successful.
