DTC Description

The ECM monitors the rich-lean switching time of the rear heated oxygen sensor (HO2S) after fuel cut-off, in order to validate dynamic behavior of rear heated oxygen sensor (HO2S). After detection of a fuel cut-off engine operating state, the ECM measures the 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 exceeds the limit value.