The HO2S is used to supply the PCM with information regarding the composition of the air/fuel mixture. The HO2S is positioned in the exhaust pipe ahead of the TWC. To measure the oxygen content, the HO2S requires a supply of ambient air as a reference. The HO2S produces a voltage that varies between 0.1V and 0.9V under normal operating conditions. The Powertrain Control Module (PCM) monitors this voltage and determines if the exhaust gas is lean or rich. If the voltage input at the PCM is under approx. 0.45V the exhaust is lean, and if the voltage input is over approx. 0.45V the exhaust is rich. The PCM constantly monitors the HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary.
If the staying time which HO2S output voltage is below or under the reference voltage to decide rich/lean is longer than threshold, the PCM determines that a fault exists and a DTC is stored.
Item | Detecting Condition | Possible cause | |
DTC Strategy | ● O2 sensor staying time (TFB2) below or under the reference voltage to decide rich/lean is monitored. | ● Poor connection ● Air leakage ● Resistance of wire in HO2S circuit ● Incorrect fuel pressure ● Open or short in HO2S heater circuit ● Faulty HO2S ● Faulty PCM | |
Enable Conditions | ● Engine coolant > 81℃ | ||
● Engine speed 1750~3500rpm | |||
● 180mmHg<Load value< 580mmHg | |||
Threshold value | ● Time, TFB2 > 30 sec. | ||
Diagnosis Time | ● 25 sec continuous | ||
Signal Voltages | Voltage will vary between 0.1 and 0.9V |
