I have a 2001 model so I'm guessing its the same. Inside the boot to the rear you should see a round cover pop it open to reveal a hexaginal screw. Get a ratchet or socket set and just unscrew. The whole housing containing the taillight bulb will start to loosen unclip the wiring and change bulb.
In the B6 (2002) pry the cover from the rear toward the front, use an 8mm socket to remove the 1 screw. This loosens the entire lens. The far side of the lens has 2 protrusions that push into 2 rubber grommets. Pull the lens toward the back of the car. The whole bulb panel unsnaps off the lens at the sides. Remove the bulb circuit board and locate the bad (or as in my case loose) bulb.
how do you replace a taillight on a Honda 2002 Civic?
Remove the taillight assembly to gain access to the bulbs
Inside the trunk on either side of the car are entry panels to the taillights. Remove the cover and unscrew the bolts that hold the taillight onto the back of the car body. Remove the taillight assembly and replace bulb(s).
unscrew it and screw in the new bulb
a 2003 Chevy silverado taillight bulb uses a 3157
To replace a taillight bulb on a Saturn L100, first, open the trunk and locate the taillight assembly. Remove the screws or clips holding the assembly in place, then gently pull it out. Twist the bulb socket counterclockwise to remove it, replace the old bulb with a new one, and reassemble everything by reversing the steps. Make sure the new bulb is securely in place before closing the trunk.
Taillight bulb replacment/Taillight housing replacement * Remove the rear inside trunk finishing panel to access the taillight housing mounting nuts * Free the grommet for the taillight electrical harness and the three taillight housing nuts then pull off the taillight housing * Rotate the bulb socket counterclockwise and pull it out of the taillight housing * To remove the bulb from the socket pull it straight out.To install a new bulb in the socket push it straight into the socket until it stops
* Remove the rear inside trunk finishing panel to access the taillight housing mounting nuts * Free the grommet for the taillight electrical harness and the three taillight housing nuts then pull off the taillight housing * Rotate the bulb socket counterclockwise and pull it out of the taillight housing * To remove the bulb from the socket pull it straight out.To install a new bulb in the socket push it straight into the socket until it stops
could be either or, simply replace one bulb to see if that fixes it if not check the fuse
I've written it up here... http://samboutros.wordpress.com/2007/04/02/2003-audi-a4-bulb-replacement/ Steps, pictures and links to bulbs...
Basically, there are three bolts that you need to take out. Then you pull off the tailight assembly. Replace the bulb as required and then replace the taillight on the car ncmuding any bolts you removed. Refer to your owner's manual.
You can access the bulb from the trunk area (from behind). Just remove and replace, should be straightforward.