I have a 2002 Audi A6 sedan with 3.0 V6 engine. A friend used their VAG-COM unit to further diagnose a P0421 fault code (Warm up catalyst below threshold - Bank 1)that keeps coming up. The VAG-COM unit displayed an Audi code of 16805. Can anyone tell me what the Audi code is? I have changed spark plugs and the Bank 1 downstream O2 sensor. I assume the Audi code is more explicit but I do not know what the 16805 code is. Please help!!!