The oxygen sensor is an important part of car’s emissions system and has been since the initial use of ECUs. The O2 sensors were created to keep tabs on how much oxygen is in your vehicle’s exhaust stream checking for efficiency confirming that the catalytic converter is functioning properly.

The sensor notes whether the air/fuel mixture is too lean or too rich. That knowledge is sent back to the ECU which adjusts the metering and timing of the fuel to make sure your car is running on the proper mixture.

These readings change as you go up hills, accelerate, have just begun driving, change engine temperature and other elements.