Circuit/System Description

The catalytic converter must be warmed to efficiently reduce the emissions. The cold start strategy is to reduce the amount of time it takes to warm the catalytic converter. 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:

• The throttle position (TP) sensor
• The manifold absolute pressure (MAP) sensor
• The barometric pressure (BARO)
• The mass air flow (MAF) sensor
• The engine coolant temperature (ECT) sensor
• The intake air temperature (IAT) sensor
• The fuel injector pulse width modulated (PWM) control
• The ignition control

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