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 devicesOverhauling the rear wheel
Inspect the condition of the rear wheel.
As the wheel rim has no bearings, it should be supported using the service tool
code 88713.2951.
Note
This service tool can also be used to install the wheel on a balancing
machine.
Overhauling the wheel
Inspect the wheel as described below.
...
Tester power supply
The dds (1) part number 97900.0215 Can be powered from the vehicle as
follows:
From the mains power supply: by connecting the power supply connector
(n) to the network power supply (2) part no.
97900.0224;
From the motorcycle: connecting the corresponding cables (see paragraph
...
Display background colour (automatic adjustment)
Instrument panel background colour is set automatically
according to exterior lighting conditions.
When sensor detects "poor lighting" (night), it switches to
black background mode; vice versa when a "significant"
lighting is detected (day), it switches to white background
...