interpreting codes & O2 sensors

I have a 96 Blazer, 4.3 eng. Service Engine Soon light stays on. I had the codes ran and it came back po153 (Bank 2 Sensor 1 Slow response), po154 (no activity), & p1153 (Insufficient switching Bank 2 sensor 1). I'm guessing I need to replace one or more of the 02 sensors? Which one is it referring to as the "Bank 2 Sensor 1". Thanks a lot for the help!!

Driver and Pass sides of engine are banks 1 and 2. Upstream sensors which are before the catylictic converters are Sensor 1's and Downstream sensors after the cats are Sensor 2's. Should be a Passenger side Upstream sensor that needs replaced. Although if one goes out, you should replace two at a time. That's just an opinion though. Try www.oxygensensors.com and buy the Denso brand. I believe thats who actually makes the OEM one. -Chris

On chevy's with single cats bank 1 sensor 1 is the closest to the engine on drivers side, bank 2 sensor 1 is the closest on the passenger side. Bank 1 sensor 2 is the one on the engine side of the catalytic and bank 1 sensor 3 is the one after the cat