Oxygen Sensor: Description and Operation

Fig. 21 Oxygen Sensor (Three-Wire Type):

Fig. 64 Oxygen Sensor With Internal Heater:

Fig. 20 Oxygen Sensor Voltage:

An oxygen (Lambda) sensor Fig. 21 and 64, 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 gases is directly proportional to the air/fuel ratio of mixtures entering the engine. The sensor, mounted in the exhaust stream, reacts to the oxygen remaining in the exhaust gases and produces a variable voltage signal (0-1.0 vdc) depending upon the oxygen content. A rich mixture will produce a high voltage (up to 1.0V) and a lean mixture will produce a lower voltage, Fig. 20.
The heated oxygen sensor has an internal heating element built into the sensor. It has three wires going to the sensor.