Bank 2 is the passenger's side of the engine and sensor 2 is behind the catalytic converter on that side.
passenger side, before catalyst converter.
That is the O2 sensor behind the catalytic converter.
on the transmission housing appx 12o'clock
Driver's side, after the catalytic converter.
it is the upper stream o2 sensor before the convertor
P0422 Main Catalyst Efficiency Below Threshold (Bank 1) oxygen (O2) sensor is bad!
That is the O2 sensor that is screwed into the front of the catalytic converter.
where is the bank1 o2 sensor at and how do i change it please i need your help
its where the #1 cylinder is that's bank one
Assuming you mean P0135, that would be O2 sensor heater circuit malfunction (bank 1 sensor 1). If the wiring to bank 1 sensor 1 is not damaged, it is probably a bad bank 1 sensor 1 O2 sensor. Replace it.
The bank 1, sensor 3, O2 sensor would be the O2 sensor post cat.
The bank 2 pre cat O2 sensor is in the rear exhaust manifold, the bank2 post cat O2 sensor is under the car after the catalytic converter, P/S nest to transmission.