Abstract: The invention relates to a high-voltage system (1) for a motor vehicle (26), comprising a high-voltage battery (2) that supplies at least one load (4), in particular an inverter (5), by means of cables (3), wherein at least one switching means (8, 9, 11) is provided in order to disconnect the high-voltage supply, a capacitor (7) connected in parallel with the load (4), and a discharge circuit (12) for discharging the capacitor (7), said discharge circuit having a discharge resistor (13) and a discharge switching means (14) that closes the discharge circuit, wherein a diagnostic device having a measuring device (16) for measuring a voltage profile that describes the voltage profile on the capacitor (7), in particular during the discharge process (17), and a control device (15) for evaluating the voltage profile in regard to a malfunction of the high-voltage system (1) is provided.