Deceleration Mode
WARNING: This page is about a different car, the 2003 Saturn LW200 and 2003 Saturn L200. However, it is still accessible from the selected car via links, so may be relevant.
When the driver releases the accelerator pedal, air flow into the engine is reduced. The PCM reads the corresponding changes in TP, MAP, and 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.