SOME VEHICLES MAY EXPERIENCE THE MIL ON WITH DTC P0139 (HO2S CIRCUIT MALFUNCTION) STORED IN PCM MEMORY. THE PCM:1.MONITORS FOR A TIME-OUT MALFUNCTION (WHEN HO2S REMAINS ABOVE 0.2V FOR LONGER THAN A SPECIFIED PERIOD OF TIME DURING FUEL CUT CONTROL).2.MEASURES THE AMOUNT OF TIME FROM WHEN CONDITIONS ARE MET UNTIL HO2S OUTPUT VOLTAGE DROPS BELOW 0.2V.3.DETERMINES A HO2S TIMEOUT MALFUNCTION WHEN THE DETECTED TIME IS MORE THAN 4 SECONDS FOR 2 OF 3 TIMES.THIS MAY BE CAUSED BY CARBON FORMING INSIDE THE ELECTRIC THROTTLE BODY (ETB) WHICH:1.REDUCES THE AIR INTAKE AMOUNT DURING DECELERATION (WITH FUEL CUT).2.ALLOWS FUEL TO REMAIN AROUND THE HO2S.3.CAUSES DETECTION OF P0139 (HO2S TIME-OUT FAIL).
