Due to possible oxygen sensor defects (e.g. reference air poisoning) or faults in the injection system (e.g. leaking fuel injector), the rear oxygen sensor may not provide the expected lean or rich signal level during fuel cut-off or full load condition. Hence, the oxygen sensor signal is checked for plausibility during this engine operating states.There are 2 cases which DTC P0140 sets.
(I) Signal monitoring during fuel cut-off: The PCM monitors rear O2 sensor signal level during fuel cut-off which normally shows near 0V and sets DTC P0140 when signal level is too high.
(II) Signal monitoring after fuel cut-off: The PCM monitors rear O2 sensor signal level after leaving fuel cut-off and sets DTC P0140 when signal remains at or below 0.6V.
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Signal Plausibiliy with lean mixture(During Fuel Cut Off) | 1. Poor Connector Connection 2. Defected Downstream O2 Sensor |
Enable Conditions |
•
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
•
Integrated mass air flow since last fuel cut off more thann 500 g
•
Integrated mass air flow since fuel cut off begin more than 12 g and less than 250 g
•
Battery voltage higher than 11 V and lower than 16 V
•
No relevant DTC present | |
Threshold Value |
•
Downstream O2 Sensor Voltage higher than 0.2V | |
Diagnostic Time |
•
5 sec. | |
Mil On Condition |
•
2 Driving Cycle |
