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1. A control unit circuit for a motor vehicle, wherein the control unit circuit comprises a control unit for providing a vehicle function and, outside a housing of the control unit, an electrical energy store for an emergency supply of the control unit, wherein the energy store is set up to supply the control unit with electrical energy if there is no supply current from an on-board electrical system of the motor vehicle, wherein, to form a circuit for the emergency supply, two electrical poles of the energy store are connected to the control unit via a cable and, in the control unit or in the energy store or on the cable, one of the two electrical poles is connected via a switching element to a ground potential of the on-board electrical system and at least one measurement circuit couples each one of the poles to the ground potential and is set up to generate a measurement signal, which is correlated with a voltage dropped between the respective pole and the ground potential, and a control circuit of the switching element is set up to keep the switching element in an electrically conductive state in normal operation of the control unit and, at least in an event that the respective measurement signal of the at least one measurement circuit indicates that the respective voltage is greater than a predetermined threshold value, to switch the switching element to an electrically non-conductive state and thus to suppress an electrical coupling, brought about by the electrical switching element, between the control unit circuit and ground potential.
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