in the exhaust manifold or before the catalic converter
The bank 1, sensor 3, O2 sensor would be the O2 sensor post cat.
You did not specify which O2 sensor it is. Is it sensor 1 bank 1, sensor 2 bank 2, sensor 2 bank 1, or sensor 1 bank 2. There are four O2 sensors on a mazda 626
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.
P0137 = O2 sensor circuit low volts (bank 1 sensor 2). Could be a faulty B1 S2 O2 sensor.
exhaust pipe
Bank 1 is the bank of cylinders that contain the number 1 cylinder. O2 sensor 1 is the first O2 sensor in the exhaust system between the engine and the catalytic converter.
Is this bank 2 sensor 1 or sensor 2?
Bank 1 is the bank of cylinders that contain cylinder 1. The O2 Sensor 1 is the O2 sensor located in the exhaust system between the cylinder head and the catalytic converter, also known as the "upstream" O2 sensor.
That would be the O2 sensor after the catalytic converter.
It is O2 Sensor Circuit Malfunction possibly (bank 2 Sensor 2) Yogi karki It is O2 Sensor Circuit Malfunction possibly (bank 2 Sensor 2) Yogi karki
P0130 = O2 sensor circuit malfunction (bank 1 sensor 1) P0150 = O2 sensor circuit malfunction (bank 2 sensor 1)