The oxygen sensor or O2 sensor is a probe that rests in the exhaust of a vehicle. This sensor measures the amount of oxygen that is mixed into the exhaust gases that result from the combustion process. This reading is sent to the Engine Control Unit (ECU), so that it can adjust the amount of air/oxygen delivered to the engine to attain the perfect air-fuel ratio. The oxygen sensor, hence, is a vital part in improving the efficiency of the engine. It generates its own voltage. Oxygen sensors affect various engine processes such as engine timing and engine combustion intervals.
If an oxygen sensor has reached the end of its life, it will begin to give false readings due to oil burn off or other debris coming from the motor. The accuracy of the sensor can also be affected if leaded gasoline is used in a non-leaded vehicle or if air leaks are present in the exhaust manifold. Oxygen sensors are usually replaced between 30,000 to 50,000 miles or as advised by the manufacturer. A bad oxygen sensor will allow the engine to run lean/rich, causing increased emissions. Common symptoms of a faulty sensor include engine pinging, poor fuel economy, rough idling and loss of power.