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 spark timing is altered to allow the catalyst to warm quickly. This diagnostic monitors the following to build an exhaust energy model:

• Spark advance
• Engine airflow
• Engine coolant temperature
• Engine run time

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