Oxygen Sensor: Description and Operation

Oxygen Sensor:

PURPOSE
Informs the ECM of the oxygen content in the exhaust gas.

LOCATION
In the exhaust pipe, upstream of the convertor.

OPERATION
The oxygen sensor provides a signal that is factored into ECM air/fuel ratio calculations and adjustments. The sensor generates a voltage based on the amount of oxygen in the exhaust gas as compared to outside air, thereby determining the rich or lean condition of the incoming air/fuel mixture. As exhaust gas oxygen content rises (lean mixture) voltage drops. Conversely, as oxygen content falls (rich mixture) voltage rises. Voltage generated by the sensor varies between approximately 0.1V and 1.0V.

CONSTRUCTION
The oxygen sensor is made of zirconium dioxide ceramic. Both inner and outer surfaces are coated with a thin layer of platinum. The sensor is installed in the exhaust manifold so that the inner surface is exposed to exhaust gases and the outer surface is in contact with outside air. The difference in the amount of oxygen contacting each surface results in voltage being generated. The ECM interprets the voltage signal as either rich or lean and makes appropriate air/fuel ratio adjustments. ECM adjustments are rapid and continuous while the system is operating in "Closed Loop." To operate properly, the oxygen sensor must be thoroughly warmed up.