Electrical on-board power supply system diagnosing method for motor vehicle, involves detecting defect when difference between three actual voltages of respective energy sources and generator is smaller than preset threshold

摘要

The method involves connecting main and auxiliary energy sources (20, 40) with a generator (30) by switching elements (25, 42). One of the energy sources is separated from the generator during driving operation, and a voltage (Ug) of the generator is increased to a voltage value, which is higher than an open-circuit voltage of the energy sources. Actual voltages (Ubat, Uh) of the respective energy sources and the actual voltage (Ug) are determined and are compared with each other. A defect is detected when a difference between the three actual voltages is smaller than a preset threshold. An independent claim is also included for an arrangement of diagnosing an electrical on-board power supply system of a vehicle.