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 devicesGeneral safety rules
Carbon monoxide
When a maintenance operation must be performed with the engine running, maker
sure that the working area is wellventilated.
Never run the engine in an enclosed space.
Warning
Exhaust fumes contain carbon monoxide, which is a poisonous gas that
can cause unconsciousness or e ...
Removal of the licence plate holder
Disconnect connector (5) of the number plate holder wiring from the main one.
Release the number plate holder light cable from the ties and the cable grommets
as indicated in sect- 7 - 6, flexible
wiring/hoses positioning, since the cable is together with the rear abs sensor
cable.
...
Removal of the control unit
Loosen the screws (1) and remove the relay supporting bracket (2), disconnect
the connectors (3) and remove the control
unit (4) from the vehicle.
...