Oxygen Sensor: Description and Operation

Right Bank Oxygen Sensor Circuit Wiring Diagram:

Left Bank Oxygen Sensor Circuit Wiring Diagram:

Purpose:
These sensors monitor atmospheric air versus exhaust gas oxygen content to produce a voltage output. This voltage ranges from approximately 0.1 volt (high oxygen - lean mixture) to 0.9 volt (low oxygen - rich mixture). By monitoring the oxygen sensor output voltage, the computer can determine the amount of oxygen in the exhaust gas and adjust the air/fuel mixture accordingly.

Operation:
The oxygen sensor is essentially a small variable battery, it has the ability to produce a low voltage signal that feeds information on engine exhaust oxygen content to the ECM. Constructed from zirconia/platinum the sensor conducts electricity under certain conditions.

At operating temperature the element becomes a semiconductor. A platinum coating on the outer surface of the element stimulates further combustion of the exhaust gases right at the surface, this helps keep the element up to the desired temperature.

The oxygen sensor has an inner cavity filled with atmospheric or reference air. The atmosphere contains approximately 21% oxygen. The inner cavity acts as the positive terminal while the outer surface acts as the negative or ground terminal. The oxygen concentration differences between the reference air and exhaust gases produce small voltages. The ECM interprets these voltages as imperfect air/fuel mixture. The ECM continually alters air/fuel mixture in response to oxygen sensor voltages attempting to achieve the perfect air/fuel mixture.

Location:
An oxygen sensor is located in each exhaust manifold.