See attached memo.
This is an on going problem with the a6 (c6) platform. if you have your parking brake light on, whether it be random or constant it is more than likely the parking brake module located in the trunk on the right hand side behind the side panel carpet. this is a well known issue that should have been considered a recall. i have seen plenty of audi's with the electronic parking brake have this failure. however it is an easy fix and about a 100-and up part (i bought mine used for 120). but i think this should be a recall.