Oxygen Sensor: Description and Operation

HEATED OXYGEN SENSOR 1 (FRONT)







Component Description
The heated oxygen sensor 1 (front) is placed into the front tube. It detects the amount of oxygen in the exhaust gas compared to the outside air. The heated oxygen sensor 1 (front) has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1 V in richer conditions to 0 V in leaner conditions. The heated oxygen sensor 1 (front) signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1 V to 0 V.

HEATED OXYGEN SENSOR 1 HEATER (FRONT)




System Description
The ECM performs ON/OFF control of the heated oxygen sensor 1 heater (front) corresponding to the engine speed.

HO2S1 Heater (Rear)




Component Description
The heated oxygen sensor 2 (rear), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas. Even if switching characteristics of the heated oxygen sensor 1 (front) are shifted, the air fuel ratio is controlled to stoichiometric, by the signal from the heated oxygen sensor 2 (rear).

This sensor is made of ceramic zirconia. The zirconia generates voltage from approximately 1 V in richer conditions to 0 V in leaner conditions.

Under normal conditions the heated oxygen sensor 2 (rear) is not used for engine control operation.

HEATED OXYGEN SENSOR 2 HEATER (REAR)




System Description
The ECM performs ON/OFF control of the heated oxygen sensor 2 heater (rear) corresponding to the engine speed.