O2 sensor

I posted this question before, so sorry for the redundancy but hopefully this time it will catch the eye of someone who might be able to help me out! I have a 97 s-10 blazer/4.3/ 4x4. I got a p0420 code that reads catylst effeciency below threshold (bank one). My question is witch O2 senor is the bank one? Thanks for any help, Woody

The P0420 means that the catalytic convertor isn't working as good as it should. The system monitors the 02 readings before and after the cat. When it shows that the cat isn't performing properly, it will set the P0420 code.

Bank1 is the driver side exhaust, bank2 is the passenger side exhaust. For systems that have a single oulet, after they meet at the y-pipe, it is then refered to as Bank1 the rest of the way back.

Your O2 sensors have the following names:


Three O2 system with single exhaust (most common):

Driverside manifold = Bank 1 Sensor 1
Passenger side manifold = Bank 2 Sensor 1
Sensor after the cat = Bank 1 Sensor 2 (correct name) or Bank 2 Sensor 2 (not correct but also okay)


Four O2 System with single exhaust:

Driverside manifold = Bank 1 Sensor 1
Passenger side manifold = Bank 2 Sensor 1
Sensor before the cat = Bank 1 Sensor 2 (correct name) or Bank 2 Sensor 2 (not correct but also okay)
Sensor after the cat = Bank 1 Sensor 3 (correct name) or Bank 2 Sensor 3 (not correct but also okay)


Dual exhaust:

Driverside manifold = Bank 1 Sensor 1
Driverside after cat = Bank 1 Sensor 2

Passengerside manifold = Bank 2 Sensor 1
Passengerside after cat = Bank 2 Sensor 2

Thanks that should help!