Ducati DIAVEL Owner's Manual page 126

To store the entered new PIN, press the reset button
(4) for 3 seconds with "MEMORY" indication
highlighted in green.
As a confirmation of the new PIN storage, the display
will show message "MEMORIZED" for about 2
seconds and then "EXIT" is automatically highlighted.
To exit the setting function, press the reset button (4)
when "EXIT" is highlighted.
Note
You can change your PIN CODE for an unlimited
number of times.
125