Oxygen Sensor: Description and Operation

Heated Oxygen Sensor:

PURPOSE
The Heated Exhaust Gas Oxygen (HEGO) detects the presence of oxygen in the exhaust system and produces a variable voltage according to the amount of oxygen.

LOCATION
Threaded into the exhaust manifold with a sampling tip extending into the exhaust stream.

CONSTRUCTION
The sensor is a zirconium dioxide ceramic thimble with a platinum surface electrode.

OPERATION
The ceramic thimble is oxygen ion conductive and generates voltage due to oxygen content difference between the atmosphere and the exhaust gas.

The sensor will generate a voltage signal between 0 volts (lean condition) and 1.1 volts (rich condition). The ECA reads this signal to achieve an air/fuel ratio of 14.7:1 when operating in "CLOSED LOOP".

The HEGO sensor must operate above 600°F. To quickly heat up the sensor, a heating element is incorporated into the sensor.

The HEGO sensor will also set a fault code when the ECA determines the output signal to be out of the normal operating range.