DTC P0139: O2 Sensor Circuit Slow Response (Bank 1 Sensor 2): DTC Detecting Condition

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