Saxat ur avsnitt 4, General requirements:
4.1 The system type shall be either a fully insulated d.c. system or a two-wire system with negative ground. Engine-mounted wiring systems can use the engine block as a grounded conductor.
For d.c. systems with a negative ground, the main grounding/earthing point shall be either:
a) the engine negative terminal, or
b) a main grounding bus of sufficient current carrying capacity.
Ovanstående är från 2012 års version av ISO 10133. Har du information om att detta ändrats i senare versioner, så vore det intressant att få veta hur.