Deceleration Mode

When the driver releases the accelerator pedal, air flow into the engine is reduced. The control module monitors the corresponding changes in the throttle position, the mass air flow (MAF), and the manifold absolute pressure (MAP). The control module shuts off the fuel completely if the reduction in speed is very fast or occurs under a long period, e.g. long engine braking downhill. The fuel is shutoff to prevent damage to the catalytic converters.