The 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 PCM 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 |
•
Catalyst Oxygen Storage Capacity Monitoring | 1. Poor Connector Connection 2. Air leak in Exhaust System 3. Defected Downstream O2 Sensor 4. Defected Three-way Catalyst Converter |
Enable Conditions |
•
Engine Coolant Temp.(ECT) higher than 165.2℉(74℃)
•
Catalyst Temp. model higher than 1022℉(550℃) and lower than 1706℉(930℃)
•
Vehicle speed higher than 3 mph(4.83 km/h)
•
Mass Air Flow more than 0.3 g/rev and less than 1.0 g/rev
•
Ambient pressure model more than 10 psi(0.7bar)
•
Canister load less than 0.5
•
Lambda Control active and lambda set-point equal to 1
•
Stable driving condition
•
Downstream O2 Sensor operative readiness detected(Downstream O2 sensor voltage lower than 0.25V or higher than 0.56V & Downstream O2 sensor max heating finished or Downstream Exhaust gas Temp. model higher than 842℉(450℃)
•
Downstream O2 sensor pre-heating phase finished
•
No opening/closing of canister purge valve
•
Battery voltage higher than 11 V and lower than 16 V
•
No relevant DTC present | |
Threshold Value |
•
Average malfunction index greater than 1 | |
Diagnostic Time |
•
30 Lambda Controller Cycles | |
MIL On Condition |
•
2 Driving Cycle |
