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/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 |
•
Check Catalyst Oxygen storage capacity (FTP75 HC or NOx emissions > 1.75*120kmi ULEV threshold) | 1. Exhaust system 2. Downstream O2S 3. Catalyst converter |
Enable Conditions |
•
1300rpm < Engine speed < 3000rpm
•
20 < Engine load < 75 %
•
600℃ < Catalyst temp < 850℃
•
Fuel system status = Closed loop
•
Time after engine start > 260sec
•
Delta temp of Catalyst < 40℃ | |
Threshold Value |
•
Amount of Oxygen Storage < 30mg | |
Diagnostic Time |
•
4 Cycles of Lambda Setpoint steps (Rich to Lean) | |
MIL On Condition |
•
2 Drive Cycles |
※ S1 : upstream oxygen sensor / S2 : downstream oxygen sensor
