LW100 L4-2.2L VIN F (2002)
Oxygen Sensor: Description and Operation
Heated Oxygen Sensor 2 (HO2S-2)
Heated Oxygen Sensor 2 (HO2S-2)
HO2S-2 is located behind the catalytic converter. The function of the sensor is to monitor the efficiency of the catalytic converter. The sensor is a
four-wire sensor. Two circuits are used for the heater and the other two are used for the oxygen sensor signal. The HO2S-2 is an electrical source that
responds to oxygen content in the catalytic converter. When the sensor reaches approximately 316°C (600°F), it produces a voltage based on the
difference in oxygen between the atmosphere and exhaust gas. The PCM sends a bias voltage (425-460 mV) on the signal line, which can be read on the
Scan tool when the sensor is cold. When the HO2S-2 is cold, it produces no voltage and has extremely high internal resistance. However, when the
sensor heats up, it produces voltage that overrides the bias voltage. This voltage in conjunction with the heated oxygen sensor 1 (HO2S-1) signal voltage
is read by the PCM to determine the efficiency of the catalytic converter. Under normal conditions, low sensor voltage means high oxygen content/lean
air-fuel mixture and vice versa. Normal sensor readings at steady cruise with a properly functioning catalytic converter will be steady around 500-800
mV.
