i went autozone to see why my check engine light in on, and the code came up as po156, the o2 sensor after the cat but he said theres four of them, i think he doesnt know what hes talking about, but this is my first audi

 

P0156
02 Sensor Circuit Malfunction (Bank 2 Sensor 2)

 

what does that mean does the sensor need to be replaced?

 

if so what kind should i go with, the dealership, if so how much

 

what car year, we need more info? Help me to help you!

 

97 a4 2.8

 

Dealer item, no generics available that don't cause problems. They are pricey too, $120 or so too.

 

so jest, if i go with a custom built exhaust with a single cat, am i going to trip the CEL?

i was going to have them put two post-cat sensor bosses on the single cat...but i guess that won't help if i'm using aftermarket O2 sensors (i can't afford 300 bucks for O2 sensors, that's just crazy)

 

Yeah you'll trip a CEL unless your post cat piece has a double bung.

 

right, that's what i'm going to do...but you're saying for the 12Vs there aren't any aftermarkets for a reasonable price?

if it means saving a few hundred bucks, i'd be willing to deal with a CEL as long as it still functions ok...i can reset the light myself, that's not a problem.