Ducati Diavel Carbon Owner's Manual page 130

The key contains a battery that must be replaced
when the low key battery "warning" is displayed as
soon as the instrument panel is turned on.
Note
In this case, replace the battery as soon as
possible.
When the charge level goes below a certain limit, the
key can only work in passive mode, like the passive
key: in this case, the instrument panel will not display
any message.
128
Attention
Do not ride with the key (active or passive)
inserted in the lock of the tank cap or in the seat lock
as it could come out and represent a potential danger.
Furthermore, if bumped, the key mechanism and the
integrated circuit could be damaged.
Also riding in poor weather conditions with the key
inserted could cause damage to its integrated circuit.
Do not leave the key on the motorcycle when it is
being washed; it is not watertight and could be
damaged.
Fig 72