PURPOSE: To enable a vehicle to be diagnosed with low cost by attaching exchangeably a central control process means for a vehicle information providing apparatus to a control process section and a central control process means for a vehicle diagnosing apparatus through a connector in diagnosis.

CONSTITUTION: A central control process means 2590 for a vehicle information providing apparatus is normally provided between input/output interfaces 2550, 2620 to function as a drive computer D/C. Here, when a vehicle has some troubles, a central control process means 2580 prepared for a vehicle diagnosing apparatus is exchanged for the central control process means 2590 through connectors 2600, 2610 to function as a vehicle diagnosing apparatus. Thus, sensors, input/output interfaces, indicators, etc. for the vehicle information providing apparatus are commonly used so that the vehicle does not normally need to be equipped with a large-scaled central control process section for diagnosis. Also, diagnosis with more extensive range and higher accuracy can be carried out by incorporating exclusive sensors and interfaces in the central control process section for diagnosis.