The ECM/PCM calculates oscillation size of rear HO2S signal which represents catalyst conversion properties. This oscillation size will determine if catalyst conversion is low due to aging or poisoning from leaded fuel or misfiring. The ECM sets P0420 if the average of calculated oscillation size of rear HO2S signal during predetermined duration is higher than the predetermined threshold.
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Oxygen storage capacity monitoring | 1. Poor connector connection 2. Air leak in exhaust system 3. Faulty downstream O2 sensor 4. Faulty Three-way Catalytic Converter |
Enable Condition |
•
Engine speed is at between 1600rpm and 3600rpm
•
Engine load is at between 25% and 80%
•
Catalyst temperature (model) is higher than 450℃(842℉)
•
Closed loop control
•
No misfire detected
•
No O2 sensor, PCSV and fuel system fault present | |
Threshold Value |
•
Deviation of amplitude of downstream O2 sensor signal and model amplitude is higher than 0.70 | |
Diagnosis Time |
•
80 sec. | |
MIL ON Condition |
•
3 driving cycles |
