A device for detecting the insulation resistance of a high-voltage battery system of a motor vehicle that includes a high-voltage battery and a high-voltage component which is operatively connected to terminals of the high-voltage battery via converters. The device includes a reference resistor operatively connected to the terminals of the high-voltage battery via switches, with a voltage measurement device configured to detect the voltage present between each respective terminal and a reference potential of the vehicle; a voltage measurement device configured to measure the voltage between the terminals; and a coupling circuit configured to monitor the high-voltage component when the contactors are open.