| VERACRUZ(EN) >2008 > G 3.8 DOHC > Fuel System > Engine Control System > Heated Oxygen Sensor (HO2S)>Repair procedures |
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FUNCTION
AND OPERATION PRINCIPLE
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 PCM. When A/F ratio is
rich or lean, 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
PCM duty signal. When the exhaust gas temperature is lower than the
specified value, the heater warms the sensor tip.
SPECIFICATION
WAVEFORM
Fig1) The signal
waveforms of front HO2S(the upper) and heater(the lower) at
idle
Fig2) The signal
waveforms of rear HO2S(the upper) and heater(the lower) at
idle
The HO2S requires a
minimum temperature to provide a closed loop fuel control system. So the
HO2S contains a heater element to reduce its warm-up time and ensure its
performance during all driving conditions. The PCM controls this heater
element by duty cycle. The main relay supplies voltage to the heater and
the PCM provides a ground circuit for activating the heater.
SCHEMATIC
DIAGRAM
COMPONENT
INSPECTION
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