Went to the parts store and they did not have any downward O2 sensors available... Dealer item only? The guy at the parts store said his light for whatever car he drives has been on for 4 years and it shouldn't rob performance from the engine but it doesn't seem like it has the power that it should.

 

Check Rock Auto. I think I saw them listed there.

 

Assuming you mean the "after-cat" O2 sensor, it has little if any effect on the operation of the engine. The factory manual indicates there is a minor impact on the A/F mixture, but I don't think anyone has actually noticed any change when the SES light comes on for the after-cat sensors.

What is the EXACT numerical code (Pxxxx)? There are codes for both the cat performance, as measured by the sensor, and for the sensor itself.

Here are the AC Celco part numbers, courtesy of Shoebox:

1996-1997 rear heated oxygen sensor
AC-Delco # AFS97

GM # 19178921 (old) 25312196

Should be available over the counter.

 

Thanks, I'll check more parts stores and then the dealer... since it isn't very important, we'll do other things first

 

How do you know it's the sensor and not the cat?