Patent attributes
In an on-vehicle network diagnosis system, a master data storage stores master data, which includes reference connection information of a plurality of electronic control apparatuses with respect to an on-vehicle network. Current connection information of the plurality of electronic control apparatuses with respect to the on-vehicle network is obtained based on a response, which is transmitted from the plurality of electronic control apparatuses in reply to a response request. A validity of a connecting state of the plurality of electronic control apparatuses relative to the on-vehicle network is diagnosed by comparing the current connection information with the master data and thereby determining whether the current connection information matches with the master data.