Except California

Oxygen Sensor Construction and Operation:

PURPOSE
The Engine Control Module (ECM) uses the O2 signal to correct fuel mixture by changing injector duration as required.

CONSTRUCTION
The sensor uses zirconia and platinum to compare exhaust oxygen content with that of the outside air.

OPERATION
The Oxygen Sensor is mounted to the exhaust manifold or pipe with the sensor end extending into the exhaust stream. When heated by exhaust gases, the sensor supplies a low voltage signal (0.0 - 1.0 volt) 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.

Oxygen sensor operation is monitored by the Engine Control Module (ECM) and a malfunction should be accompanied by a Diagnostic Trouble Code (DTC). Circuit and output testing procedures are covered in detail in the Diagnostic Trouble Code Charts. Testing and Inspection

Oxygen Sensor malfunctions will cause increased emission output and smog check failure. Other symptoms may include poor idle quality or poor fuel economy.

HINT: When monitoring oxygen sensor operation with an oscilloscope, watch for a sine wave with a frequency of at least 8 cycles in 10 seconds. A "lazy" oxygen sensor will not always set a code, but will usually cause abnormal emissions levels.