Bad O2 sensor? which one is

[fedie]

Hi I have a '02 A4 3.0 and getting this from Vagcom

1 Fault Found:
16805 - Warm Up Catalyst: Bank 1: Efficiency Below Threshold
P0421 - 001 - Upper Limit Exceeded - Intermittent

Does anyone knows if this its a bad O2 and which one is?

Thanks

[fedie]

up

[onceover]

not sure what side bank 1 is, call your dealer.

my friend had his go and the code said B1S1, so it told you that it was the sensor before the cat, your code doesnt really tell you much...