Deceleration Mode

When the driver releases the accelerator pedal, airflow into the engine is reduced. The powertrain control module (PCM) reads the corresponding changes in throttle position (TP), manifold absolute pressure (MAP), and mass air flow (MAF). The PCM shuts OFF fuel completely if the deceleration is very rapid, or for long periods, such as long, closed-throttle coast-down. The fuel shuts OFF in order to protect the catalytic converters.