#1 cylinder is on the left side so bank 2 is the right side sensor 1 is before the cat sensor 2 is after the cat
Is this bank 2 sensor 1 or sensor 2?
The bank 1, sensor 3, O2 sensor would be the O2 sensor post cat.
It is the sensor below the catalytic converter.
This would be the sensor after the catalytic converter.
3, sensor 1 bank 1, sensor 2 bank 1, sensor 2 bank 2
Bank 2 is the passenger side exhaust pipe and sensor 2 will be the closest sensor to the converter.
You need to change the upstream sensor
That would be the O2 sensor after the catalytic converter.
usually bank 1 is the bank with # 1 cylinder in it and sensor # 1 is the front o2 sensor(usually in the manifold). You will need a O2 sensor socket or a 22mm wrench or deep socket.
Assuming this is a V-6, bank 1 sensor 1 would be the first O2 sensor in the exhaust on the drivers side of the engine.
That is the O2 sensor behind the catalytic converter.
Bank one sensor one oxygen sensor