Oxygen Sensor: Description and Operation

System Description:

Operation:

HO2S1 HEATER
The ECM performs ON/OFF control of the heated oxygen sensor 1 heaters corresponding to the engine speed.

System Description:

Operation:

HO2S2 HEATER
The ECM performs ON/OFF control of the heated oxygen sensor 2 heaters corresponding to the engine speed.







HO2S1
The heated oxygen sensor 1 is placed into the exhaust manifold. It detects the amount of oxygen in the exhaust gas compared to the outside air. The heated oxygen sensor 1 has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. The heated oxygen sensor 1 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 1V to 0V.




HO2S2
The heated oxygen sensor 2, after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank.

Even if switching characteristics of the heated oxygen sensor 1 are shifted, the air-fuel ratio is controlled to stoichiometric, by the signal from the heated oxygen sensor 2.

This sensor is made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. Undernormal conditions the heated oxygen sensor 2 is not used for engine control operation.