Fault Detection

If the passive test detects a storage capacity significantly above the borderline limit, the catalyst is determined to be good and the monitoring is complete. If the passive test does not meet the condition for a good catalyst, the active test is initiated and the OSC is calculated. The catalyst is diagnosed by comparing the determined OSC against the borderline threshold.

Monitoring conditions for active test:

• no faults with the lambda sensors (signal, aging, heater)
• canister purge value < limit
• no error on EGR system (if available)
• modeled catalyst temperature within range
• misfire rate < limit
• regular A/F control (not in fuel cut-off)
• engine air mass flow within range