The invention relates to a system and a method for storing data in a motor vehicle. As storage medium having a very large storage volume the invention provides for a data storage card which is assigned to the motor vehicle and housed in a vehicle-side interface designed for reading/writing into the storage card. The motor vehicle is equipped with a data bus to which the interface as well as other systems, components and sensors of the motor vehicle are connected. A vehicle-mounted error-diagnosis unit generates malfunction codes which together with other relevant data of different vehicle-side systems are constantly stored in the data storage card so as to generate permanent load profiles and are maintained throughout the service life. The stored data include data on the motor vehicle and its owner, malfunction codes reflecting the state of different systems and components of said motor vehicle, operating data, repair and service information and possibly data regarding mandatory technical checks as well as technical specifications and operating instructions. From an evaluation of these data conclusions can be drawn which are relevant for product improvements and repair strategies and indicate the performance of a motor vehicle in the field.