Oxygen Sensors: Notes

The oxygen sensors play a role in the mixture control and the exhaust analysis. It sends a signal to the Engine Control Module (ECM) indicating if the engine is running either rich or lean. The ECM uses this signal in combination with other engine management component signals to adjust mixture. This occurs only during closed loop operation.

There are two types of oxygen sensors:

• 4 wire sensors
• 6 wire sensors (broadband)

Pre-catalyst oxygen sensors monitor combustion efficiency, and are located in the exhaust before the catalytic converter.

Post-catalyst oxygen sensors monitor catalytic converter efficiency, and are located in the exhaust at the outlet of the catalytic converter.

The oxygen sensors measure the oxygen content of the exhaust to obtain an instantaneous indication of engine operation. The sensors must be at operating temperature to be accurate. Because the oxygen sensor needs to reach operating temperature quickly, a heating element is integrated into the sensor. This enable the temperature to be maintained despite changing engine operating conditions.