BMW's electric and hybrid cars run a separate high-voltage network alongside the normal 12V system: the battery management electronics (SME) watch the pack, the electric machine electronics (EME) drive the motor, and charging runs through its own unit — KLE or, on newer cars, the combined charging unit. Faults in any of them tend to surface the same way, as a drivetrain or high-voltage warning, so the message alone does not say which unit is at fault.

The most common HV fault is isolation. The system constantly measures insulation resistance between the high-voltage side and the chassis, and a drop — moisture in a connector, a damaged cable, contamination inside the drive unit — triggers warnings and can take the car off the road. The fault code points at the system; the test plan then isolates which component is leaking.

High-voltage work has a hard entry requirement: the system is disabled and locked out at the service disconnect before anything orange gets touched, and on the newest generation BMW requires high-voltage training for any component on that network. BMW EV / high-voltage trained.

Covers BMW i3 and i8, the i4/iX/i7 range and the plug-in hybrids, Mini Cooper SE, and Rolls-Royce Spectre.