Found this on Web American i know but maybe same thing
Quote"
I now own a 2000 Audi Quatro 2.8 v6 which has been in the family since new, so I have seen all the problems this car has gone thru,but still didn't want to see it go, because it's loaded and in mint condition even with 158,000 miles, so I bought it. Boy am I sorry now, Like so many others the engine light kept coming on. The Audi dealer said I needed new Cat converters to the tune of 1200 dollares each and o2 sensors . Because of what the dealer charges to supposidly fix it and only for it to come on again, I went to a local German repair
shop. Reset the check engine light and replaced 2 o2 sensors, drove it a week, light came back on.etc. Replaced the other 2 o2 sensors and reset light, drove light came back on, but the code was different. Reset codes drove all day without turning off and passed smog test. I decided since the old batterie was running down easily the shop agreed with me when the batterie loses some juice overnight it was tripping the old code back on. SO YOU MIGHT HAVE A SHORT SOMEWHERE. You could try resetting the code and use a trickle charger on it at night to keep the batterie up to the proper amps overnight <font color="red"> </font>
