To provide external access to a specification file stored in at least one memory unit, which is associated with at least one electronic control unit which may be in a vehicle, a computer is connected to a first communication bus in the vehicle. A first module in the computer is adapted to communicate with the at least one electronic control unit over the first communication bus. Provided that a user-unique key is connected to a port of the computer and a software component of this key is set to an active authorization state, the computer is enabled to communicate with the at least one electronic control unit. Thus, the computer may read out the specification file as well as update the specification file.