I have 02' A6 3.0L. Last Saturday, the "Brake Light" sign came up on my screen when I was driving on a highway; I thought it was the problem of the brake and immediately pulled over the curb, and read the manual; well it is probably the electric problem. I checked the rear light when my wife stepped on the brake, and found out the brake passenger light bulb was gone.Since only one of the stop light went away, it should not be the fuse because the fuse takes care of both lights, thus it should be the bulb. I read instruction here:
http://www.jmaguire.com/blog/2006/02/05/stoplight.html
I purchased the bulb from Auto Zone, and plan DIM. Here is what I did:
1. take off the compartment door for storage on the passenger side
2. you should see the bulb housing, find the plastic clips (which are black), and snap them, the whole bulb housing can be easily taken out.
3. Twist out the broken bulb, replace the new one, then clip it back and close the compartment door.
Voila.
It is much easier than the instruction. Not a single tool is needed.

Hope it is useful.

 

Thanks for the write up, people here a pretty sharp though.

 

DIDO , THEY SHOULD BE TECHS!!!