Heated Oxygen Sensor (HO2S) consists of zirconium and alumina
and is installed on upstream and downstream of the Manifold Catalyst
Converter (MCC).
After it compares oxygen consistency of the atmosphere with
the exhaust gas, it transfers the oxygen consistency of the exhaust gas
to the ECM. When the A/F radio is high or low, it generates
approximately 1V or 0V respectively. In order that this sensor normally
operates, the temperature of the sensor tip is higher than 370°C
(698°F). So it has a heater which is controlled by the ECM duty signal.
When the exhaust gas temperature is lower than the specified value, the heater warms the sensor tip.

Other information:
Replacement
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When installing the belt, make sure not to damage the pretensioner.
1.
Remove the front anchor seat belt (A).
?How to detach the anchor seat belt
1) Expose the red-colored indicator pin (A) by pushing the slot hole with a O 1 ...
Removal
In case of removing the high pressure fuel pump, high
pressure fuel pipe, delivery pipe, and injector, there may be injury
caused by leakage of the high pressure fuel. Do not perform any repair
work right after the engine stops.
1.
Turn the ignition switch ...