Need help with O2 sensor problem

[imq707s]

The "check engine" light on my 97 Mountaineer (same as explorer, 5.0 V8) has started to turn on every few days, and then go off. I took it to AutoZone and they scanned it for me and the guy said it's the " bank#1, sensor#2 O2 sensor". the guy didn't really give me any more info than that. He did say that I should have four o2 sensors, one on each side before that cats, and one on each side after the cats. All I can find is the two ( one on each side) before the cats. Can someone give me some more info as to which O2 sensor I need to replace. What does bank 2 sensor #1 mean? Passenger or driver side? Thanks

 

[mrboyle]

Bank #1 is passenger side, #2 is driver side.

 

[Robert]

As Mike said, bank one will be the passenger side. Look at the pipe between your catalytic converter and your muffler. That is where you will find your downstream O2 sensors.