Electrical vehicle systems are amongst the most complex systems to be found in vehicles. Diagnostics and troubleshooting in these systems are presenting ever greater challenges for workshop personnel. The use of special measuring and test equipment as well as sophisticated diagnostics systems requires specific expertise in vehicle electrics and in the complete data communication system structure. In addition to the conventional 12 V on-board power supply system, vehicles are increasingly featuring high-voltage systems in the drive system and, more recently, the comfort system too (HV air-conditioning system). This means that work on electrical vehicle systems must now also be performed in line with the mandatory safety measures set out in DGUV 200-005 and must have the required authorisation.