The PCM monitors rich-lean switching time of rear heated oxygen sensor (HO2S) after fuel cut-off to validate dynamic behavior of rear heated oxygen sensor (HO2S). After detection of fuel cut-off engine operating state, the PCM measures rich-lean switching time of the rear heated oxygen sensor (HO2S) signal and compares it to the predetermined limit value. DTC P0139 is set when the switching time is bigger than the limit value.
Item | Detecting Condition | Possible Cause | |
DTC Strategy |
•
Response Rate Monitoring | 1. Poor Connector Connection 2. Air leak in Intake or Exhaust System 3. Defected Fuel system 4. Defected Downstream O2 Sensor | |
Enable Condition | Case 1 |
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Downstream O2 Sensor operative readiness detected(Downstream O2 sensor voltage lower than 0.25V or higher than 0.56V & Downstream O2 sensor max heating finished)
•
Catalyst Temp. model higher than 752℉(400℃)
•
Downstream O2 sensor pre-heating phase finished
•
Downstream O2 sensor signal at entry into fuel cut off higher than 0.6V
•
Battery voltage higher than 11 V and lower than 16 V
•
No relevant DTC present | |
Case 2 |
•
Downstream O2 Sensor operative readiness detected(Downstream O2 sensor voltage lower than 0.25V or higher than 0.56V & Downstream O2 sensor max heating finished)
•
Catalyst purge after fuel cut off active
•
Mass air flow integral after leaving fuel cut off more than 100 g
•
Catalyst Temp. model higher than 752℉(400℃)
•
Exhaust gas Temp. model at sensor location higher than 752℉(400℃)
•
O2 sensor internal resistance less than or equal to 10000Ω
•
Battery voltage higher than 11 V and lower than 16 V
•
No relevant DTC present | ||
Threshold Value | Case 1 |
•
Ratio(Max. allowed switching time = 300 msec.) more than 1 | |
Case 2 |
•
Average of signal gradient less than 1500 mV/s | ||
Diagnostic Time | Case 1 |
•
3 valid fuel cut off phases | |
Case 2 |
•
3 valid diagnostic cycles | ||
MIL ON Condition |
•
2 Driving Cycle | ||
