2004 Audi A6 oxygen sensor coeds, what to do?

MADCOBRA03

MEMBER
2004 AUDI A6

Engine Performance problem
2004 Audi A6 6 cyl Four Wheel Drive Automatic 48.5XX miles

Hi I just pulled thre coeds from my audi's computer, P0056, P0421, P0161, I think they sensor 2 bank 2. Here is the story: I dont have catalic converters anymore, just an empty shell, they went bad at one point and I had to gut them out. Right after I gutted them out one of the coeds puped up, I think it was P0421= Warm Up Catalyst Efficiency Below Threshold. Then I got aftermarket software installed fo added boost and at the same time they recalibrated oxygen sensor sensetivity or something in that area. CEL was gone for a few days, then I put 110 octane (I have a tune for it), and now I found out that it was leaded instead of unleaded, so check engine light came back on with all of the above coeds. So what do I do now, is there a way to clen them out, or I have to by new sensor?

1 Reply

RACEFAN966

MECHANIC
5,029 POSTS

Ok these codes all point at the bank 2 sensor 2 not working. However keep in mind as this system was intended to work was with cats working meaning that the front O2's read fuel and the rear O2's read cat functions more or less in simple terms. Now with that you may from time to time have O2 and cat codes come up no mater what but that will have to just be delt with as it happens. At this point however I would say replace that one sensor and you will be good.