Oxygen Sensor: Description and Operation

Heated Oxygen Sensor:

PURPOSE
The Heated Oxygen Sensor (HO2S) monitors the oxygen content in the exhaust gases. This information is then sent to the Digifant Engine Control Module (ECM) for use in determining the proper air/fuel ratio.


OPERATION
The amount of oxygen in the exhaust varies depending on the air/fuel ratio. The sensor produces a varying voltage between 150 mV and 850 mV depending on the oxygen content in the exhaust.

The use of a heating element in the oxygen sensor allows the sensor to reach operating temperature faster. Secondly, the oxygen sensor can be placed further away from the engine to increase its service life. This is due to sensor not being subjected to the high heat produced during extended full load conditions.

Since the sensor can operate at the ideal temperature, low exhaust emissions can be reached and maintained due to a more accurate signal.

The Digifant control module (J169) uses the voltage signal from the oxygen sensor to adjust the opening time of the injectors. Depending on the signal, this will either increase or decrease the amount of fuel being delivered for combustion.

Oxygen Sensor (Lambda Sond) Voltage Vs. Exhaust Oxygen Content:

SIGNAL
The sensor signal voltage is in direct proportion to the amount of oxygen in the exhaust gases. This depends on the air/fuel ratio. A "Lambda" value of 1 represents the theoretically perfect ratio. A rich mixture results in a higher voltage then a lean mixture.

The voltage produced by the Heated Oxygen Sensor varies between 0.1 - 1.0 volts. The ECM uses this information to adjust the amount of fuel injected.