P0150 - anyone know which o2 sensor is b2 s1?
 

My car keeps setting P0150, sensor b2 s1 malfunction in circuit. Unknown error elaboration. It sets it when I come to a stop. Example, I'm driving, there are no trouble codes. I come to a stop, and after a second or two, it sets P0150. Any ideas?

Driver's side cylinder bank, pre-catalyst.

It looks like this
 

FRONT

LEFT | RIGHT
B2S1 | B1S1
CAT | CAT
B2S2 | B1S2

BACK

confirming
 

Does "LEFT" = American issue driver side?

Is there any set procedure for fixing b2s1 P0150?

Thanks - any ideas
 

Any ideas on what's causing it to set when I come to a stop?

Plugs, or vacuum?
 

Digging through the old forum postings, found one where they discussed changing spark plugs. My A4 started setting these codes after I changed the plugs. My guesses are either I messed up a vacuum line, or picked bad plugs.
Are these engines sensitive to plugs? If so, what's a good brand.
If not, I'll start looking for a leak.

Yes. Left = US driver's side. Procedure is...
 

to replace the O2 sensor. Make sure it's not just disconnected first.