Oxygen Sensor

The oxygen sensor is a special electrical switch placed in the exhaust pipe so that it can sense exhaust gas flow and measure its oxygen content. As more oxygen is sensed (showing a leaner mixture), the electrical signal generated by the switch drops in voltage. A lower oxygen content (richer mixture) causes an increase in the voltage signal.

This signal enables the computer to determine whether to richen or lean the mixture to maintain the correct air/fuel ratio. The voltage range for the ideal air/fuel mixture is around 0.45 - 0.55 volt.