DTC Description

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 3 cases which DTC P0140 sets.

1. Signal monitoring during fuel cut-off: The ECM 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.
2. Signal monitoring after fuel cut-off: The ECM monitors rear O2 sensor signal level for a certain time after leaving fuel cut-off and sets DTC P0140 when signal variation during checked period is too small.
3. Signal monitoring during full load: The ECM monitors rear O2 sensor signal during full load which applies rich air-fuel mixture and sets DTC P0140 when rear O2 sensor signal is too low.

   If same error code is set in the next driving cycle, the ECM illuminates the MIL.