The PCM uses dual oxygen sensors to monitor the efficiency of the manifold catalytic converter (warm-up catalytic converter). By monitoring the oxygen storage capacity of a catalyst, its efficiency can be indirectly calculated. The upstream (front) HO2S is used to detect the amount of oxygen in the exhaust gas before it enters the catalytic converter. A low voltage indicates high oxygen contents (lean air mixture). A high voltage indicates low oxygen contents (rich air mixture). When the catalyst efficiency drops, no chemical reaction takes place. This means the concentration of oxygen will be the same at the rear as it is at the front.
If the oxygen storage time for Bank1/2 is lower than threshold , the PCM determines that a fault exists and a DTC is stored. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till 1 driving cycle.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● Manipulates Airfuel and stores the times it takes for the pre and post converter oxygen sensors to switch. | ● Leakage in the exhaust system ● Faulty Catalyst Converter ● Faulty HO2S ● Faulty PCM |
Enable Conditions | ● Engine runtime ≥ 580 ● Purge Concentration Learned ● Airflow in range (3~10 g/s) ● Closed throttle ● Coolant temp in range ● Intake air temp in range ● Barometer above 72 kpa ● Max number of test attempts not exceeded ● Closed loop fueling ● Catalyst temperature in range ● Fuel learning in range ● Vehicle speed below 3kph (2mph) ● Auto trans in gear ● Long term fuel correction learned at idle ● Airflow timer reached limit ● Max idle time not exceeded ● Max number tests not complete ● Disabling faults not present | |
Threshold value | ● Oxygen Storage Time ＜ 1.5 sec. for Bank 1 (2 sec. for Bank 2) | |
Diagnosis Time | - | |
MIL On Condition | ● 1 Driving cycle |
