To carry out package management of diagnosis information of an engine- coolant system by a self-diagnostic function of a control unit carried in each user's vehicle and effectively utilize the same, thereby enabling an advance notice of an inspection time before occurrence of a trouble as well as improving the system reliability.

In the case of receiving vehicle information, it is discriminated and investigated whether the diagnostic judging result with trouble is included (S100 to S102). When the diagnostic judging result with trouble is included, various kinds of data are gathered to presume a portion where the trouble occurs and to determine service procedures (S103 to S105) so that corresponding parts can be prepared in advance and the service plan can be carried out smoothly. When the diagnostic judging result with trouble is not included, all the information concerning the vehicle is gathered to calculate the degradation state of parts or a system so as to presume the degradation property and lifetime thereof, thereby calculating the time at which the service is required (S106 to S110). And the time for service and the results are notified to the user and the various information is notified to the dealer and recorded on the database (S111 to S113). Thus, before trouble occurs in the engine-coolant system, the inspection: time is preliminarily announced to the user so that the cost and time required for repair are reduced.