Ducati Monster 821 Owner's Manual page 125

When you press button (4) to confirm the fourth and
last digit, the instrument panel highlights the
message "MEM" and the relevant box will start
flashing.
To save the new setting, hold button (4) for 2 seconds
while the message "MEM" is highlighted.
If settings have been saved (D), the message "MEM"
and the relevant box will be shown steady ON for 2
seconds, and then the "EXIT" box will start flashing.
If settings have not been saved, the instrument panel
highlights again the string of four dashes "- - - -" of the
new PIN to allow the rider to try again and enter a
new code.
To quit, press button (4).
Note
You can change your PIN CODE an unlimited
number of times.
124
MENU
MEM
4
1
4
2
1
2
MENU
EXIT
MEM
MENU
EXIT
MEM
D
MENU
EXIT
MEM
4
Fig. 63