Oxygen Sensor: Description and Operation

Oxygen Sensor (Three-Wire Type):

An oxygen (Lambda) sensor located at the exhaust manifold is used to provide more precise control of air/fuel mixtures. This system operates by measuring oxygen content in exhaust gases, as the amount of oxygen remaining in the exhaust gas is directly proportional to the air/fuel ratio of mixtures entering the engine.

Oxygen Sensor With Internal Heater:

The sensor, mounted in the exhaust stream, reacts to the oxygen remaining in the exhaust gases and produces a variable voltage signal (0.4 - 1.0 vdc) depending upon the oxygen content.
The oxygen sensor is also fitted with a heating element. Heating the oxygen sensor enables it to begin operation earlier, therefore, improving exhaust emissions.

Oxygen Sensor Voltage:

A rich mixture will produce a high voltage (up to 1.0V) and a lean mixture will produce a lower voltage.