Circuit/System Description

The catalyst must be warmed to efficiently reduce the emissions. The cold start strategy is to reduce the amount of time it takes to warm the catalyst. During a cold start, the engine idle speed is elevated and spark timing is retarded to allow the catalyst to warm quickly. This diagnostic monitors the following to build an exhaust energy model:

• Engine speed
• Spark advance
• Throttle position
• Engine airflow
• Engine coolant temperature
• Engine run time
• Park/neutral position
• Vehicle speed

The actual model is then compared to the expected exhaust energy model.