If you are replacing a 02 sensor with a new one I would cut off the wires at the sensor and slip a 7/8" box wrench over the sensor and remove it with a counterclockwise motion.
The bank 1, sensor 3, O2 sensor would be the O2 sensor post cat.
Remove the vacuum hose from the O2 sensor. Remove the wiring harness. Remove the O2 sensor retaining screws. Reverse the process to install the new O2 sensor.
That would be the O2 sensor located after the catalytic converter.
It screws into the catalytic converter.
on the drivers side underneath the engine by the front tire. You will notice a pigtail leading to the exhaust in this area. This o2 sensor is the main sensor, there should be a catalytic o2 sensor located after the converter.
To change an O2 sensor you need to disconnect the wiring harness from the sensor. Use an O2 sensor socket and ratchet set to remove the old sensor and replace with the new one.
A defective O2 sensor will not prevent the engine from starting. The engine will start and run albeit not as it should.
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
unscrew it
You can't.
the o2 sensor is located in the exhaust manifold. As you pop the hood and look at the engine, you should see a silver colored heat shield. Unplug the old O2 sensor. Then remove the heat shield. Its easier this way (10 MM bolts). Get a O2 sensor socket and remove the sensor and replace. The rear sensor is located in 1 0f 3 places. Either before in or after the catalytic converter. For this one you just get the O2 sensor socket and remove. (When the engine is cold) Madd Dogg 40/40
All O2 sensors are threaded into the exhaust system at various points.