Oxygen Sensor: Description and Operation

Main Oxygen Sensors:

PURPOSE
Three oxygen sensors, two mains and a sub, measure the oxygen content in the exhaust and send a voltage signal to the ECM.

LOCATION
The main oxygen sensors are mounted in the exhaust manifold, the sub directly before the catalyst.

CONSTRUCTION
Each sensor consists of a steel housing, sensor tip, and its protective sleeve. The sub-oxygen sensor also contains a heating element. The sensor tip itself is made from a platinum covered zirconium-oxide pipe.

OPERATION
A measureable voltage is generated by comparing the amount of oxygen in the exhaust gas with the amount in the ambient air.

The sensor operates only within a certain temperature range of approx. 545 - 1530°F (285 - 850°C).

The exhaust gases reach the outer surface of the oxygen sensor tip via the openings in the protective sleeve. Ambient air reaches the sensor's inner surface via channels. The differance in oxygen content produces a voltage read by the ECM.

The heating element is controlled by the ECM. When the sensor is cold the ECM grounds the circuit, causing the sensor to heat. The electric heater allows the sensor to reach operating temperature much sooner than it could simply by using exhaust gas to heat it. The heater also prevents sensor cool-down during periods of extended idling.