Dirty Throttle Body
Dirty Air Filter
Dirty Mass Air Flow (MAF) Sensor
Intake manifold leak
Damaged, restricted, modified or enhanced exhaust system
Engine Light ON (or Service Engine Soon Warning Light)
The catalytic converter must be warmed to efficiently reduce 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: Engine speed, Spark advance, Throttle position, Engine airflow, Engine coolant temperature, Engine runtime, Park/neutral position, Vehicle speed. The actual model is then compared to the expected exhaust energy model. The Diagnostic Trouble Code (DTC) will set when the actual exhaust energy model does not match the expected exhaust energy model.