What is the purpose of 02 sensor?

Answer 1

The oxygen sensor reports live information about the engine's air/fuel mixture to the power train control module. This information is used primarily to help calculate fuel delivery to the engine, which changes continuously while it is running. If the engine is running lean, the power train control module will sense this from the oxygen sensor's signal and increase the air/fuel mixture to the engine. Conversely, just the opposite occurs when the engine begins to run rich. On OBDII-equipped vehicles, the sensors are also used to help determine the efficiency of the catalytic converter. The power train control module does this by comparing the signal of the sensor located at the inlet of the catalytic converter with the signal of the sensor located at the outlet of the converter.

Answer 2

To make sure that your car's fuel system has the proper amount of air/fuel ratio. The O2 sensor senses this, and if your mixture is too rich, the computer gives the engine more air. if the mixture is too lean, the sensor tells the computer to adjust and allow less air into the engine.