Oxygen Sensor Bank 1

[jrtmouse]

2000 Pontiac Sunfire
Received CEL P0133-"P0133 Pontiac - HO2S Slow Response Bank 1 Sensor 1".

I'm looking at RockAuto for oxygen sensors.

1) Do I want "upstream" or "downstream"?
2) Where is Bank 1 vs Bank 2?
3) Is there a sensor 1 and sensor?

Just want to make sure I'm replacing the right sensor.

Thanks.

 

[Zimgxp]

Bank 1 is the side with #1 cylinder. Bank 2 is the other. You want an upstream one. Sensor 2 is after the cat. Sounds like the sensor is getting lazy, time to replace it.