An influencing device for influencing an active chassis system is provided. A roadway sensor produces sensor data relating to a roadway which is located in front of the vehicle in the direction of travel, the sensor data is used to acquire a roadway profile. A pilot control unit determines, as a function of the acquired roadway profile, a pilot control variable which is used to adapt the setting of the spring or damper units to the acquired roadway profile. A diagnostic unit acquires a deviation between the anticipated state of the vehicle and the actual, current state of the vehicle on a basis of a variable which describes the roadway profile and a variable which describes the current state of the vehicle.