The invention relates to a motor vehicle diagnostic system for acquiring and storing diagnostic data and transmitting them from control units in a motor vehicle to a computer outside the motor vehicle. The system is composed of components which are located inside the vehicle and of components which are located outside the vehicle. Using a transmission module, in which a short diagnostic test is implemented, diagnostic data from onboard components are interrogated and are transmitted via a WLAN link to the computer system of a service company. The diagnostic data of the onboard components can be further processed using the computer system. The disclosed invention is aimed in particular at assisting a service employee in the vehicle reception of a service workshop.