Oxygen Sensor: Description and Operation

Oxygen Sensor:

Oxygen Sensor:

Oxygen Sensor Operation:

PURPOSE
System uses 2 sensors to detect exhaust gas oxygen content and signal the PCME. With this signal, PCME maintains proper air/fuel ratio by controlling fuel injection quantity and purge control solenoid valve operation.

LOCATION
One sensor each in exhaust pipe below exhaust manifolds.

OPERATION
PCME determines air/fuel ratio based on oxygen sensor voltage signal and makes appropriate adjustments to maintain optimum ratio of 14.7:1.

Sensors consist of a hollow zirconia ceramic element with a platinum coating on inside and outside surfaces. The open end of the element is exposed to the atmosphere and its surface is connected to the PCME. The closed end protrudes into the exhaust stream and its surface is connected to ground. Oxygen reacts with the platinum surfaces at high temperatures. When there is a difference in the amount of oxygen reacting with the inner and outer surfaces, a voltage potential is generated. The voltage range is approximately 0.1-1.0V. Voltage increases when the concentration of oxygen in the exhaust is low (rich air/fuel ratio) and decreases when the concentration is high (lean air/fuel ratio).

Oxygen Sensor Output Voltage vs. Air/Fuel Ratio:

The difference in oxygen concentration in the narrow range of optimum air/fuel ratio causes a large voltage change that is easily measured by the PCME.

Sensor elements only react efficiently with oxygen if element temperature is around 575°F (300°C) or hotter. An electrical heating element is built into the sensors to help warm them up to operating temperature more quickly and maintain temperature during times when sensors may cool off, such as prolonged idle or decelerating.