Oxygen (O2) Sensor

The O2 sensor is located in the exhaust pipe. The voltage output from this sensor, which varies with the oxygen content in the exhaust gas, is supplied to the ECU.

The ECU utilizes it as a reference voltage to vary the fuel/air mixture ratio. The battery voltage input to the ECU is used to ensure that the proper voltage is applied to the injector. The ECU varies the voltage applied to the injector to compensate for battery voltage fluctuations.