The kickdown function
When the accelerator pedal is depressed all the way to the floor (past the normal full accelerator position), the transmission will automatically engage kickdown, i.e. immediately shift down to a lower gear.
If the accelerator pedal is released from the kickdown position, the transmission will automatically shift up again.
Safety function
The transmission control module is equipped with a downshift protection feature to help prevent the engine from overheating.
In some conditions, the transmission will prevent downshifting/kickdown if this would lead to such high engine speed (rpm) that the engine could be damaged. If the driver still attempts downshifting or kickdown at a high rpm, nothing will happen and the original gear will remain selected.
With kickdown, the vehicle can downshift one or more steps at a time depending on the engine speed. The vehicle upshifts when the engine reaches its maximum rpm to prevent engine damage.