Oxygen Sensor: Description and Operation

PURPOSE
The Heated Oxygen (HO2) Sensor, located at the exhaust pipe with the sensor end extending into the exhaust stream, supplies a voltage signal to inform the Engine Control Module (ECM) of the air/fuel mixture in the engine.
The Sub Heated Oxygen Sensor (SHO2) is used by the ECM, on California models only, to test the operation of the Catalytic Convertor by comparing readings between the HO2 and the SHO2 sensors.

OPERATION
The HO2 Sensor uses zirconia and platinum to compare exhaust oxygen content with that of the outside air. When heated by the combination of its internal heater and exhaust gases, the sensor supplies a low voltage signal to the ECM. When the engine is running rich, the oxygen differential is relatively high so signal voltage increases. When a lean condition occurs the difference in oxygen content is much lower causing a lower voltage signal to be produced.