The negative cable, which is normally connected to the negative pole of the battery, is fastened to the crankcase. From here, the cable branches off and splits up within the electrical system to carry the ground connection to the different elements in the system.

The image shows the ground connection on left side of the engine crankcase.
The battery charging circuit and power distribution
Electrical power for lighting and signalling devicesWarranty
In your own interest, and in order to guarantee product
reliability, you are strongly advised to refer to a ducati dealer
or authorised service centre for servicing that requires any
particular technical expertise.
Our highly skilled staff have the tools required to perform any
servicing job ...
Removing the silencer
Loosen the clamp (38) that retains the silencer (4) to the complete exhaust
system.
While holding the nut (8), loosen the screw (1) and remove the silencer (4)
from the motorcycle.
Loosen the screws (40) and remove the silencer guard (41).
...
Refitting the expansion tank
If the support (15) has been removed, place the hose clamps (14) on the
bracket (15) orienting them as indicated.
Fully press the pins (a) to block the clamps (14) until pins surfaces (b) are at
the same level of the clamps (14) surfaces.
Apply recommended threadlocker to the thread of the ...