an arrangement for monitoring a rotational speed sensor of an internal combustion engine having a starter and a rotational speed sensor which supplies an output signal in dependence on a rotational speed , has a unit for measuring a vehicle electrical system voltage , and a control device in which an output signal of the rotational speed sensor is related to a vehicle electrical system voltage and an error operation of the rotational speed sensor is monitored . the measuring unit and the control device are formed so that for error recognition a course of the vehicle electrical system voltage is evaluated during a starting process of the internal combustion engine , and an error recognition is released only when a typical course of a starting process for the vehicle electrical system voltage is recognized and simultaneously no output signal of the rotational speed sensor is recognized .