When the accelerator pedal is pressed all the way to the floor (beyond the position normally regarded as full acceleration) a lower gear is immediately engaged. This is known as kick-down.
If the accelerator is released from the kick-down position, the gearbox automatically changes up.
To prevent over-revving of the engine, the gearbox control program has a protective downshift inhibitor.
The gearbox does not permit downshifting/kick-down which would result in an engine speed high enough to damage the engine. Nothing happens if the driver still tries to shift down in this way at high engine speed – the original gear remains engaged.
On kick-down the car can shift down one or more steps at a time, depending in engine speed. The car shifts up when the engine has reached is maximum engine speed in order to prevent engine damage.