On the condition that a predetermined time has passed after an engine control unit stops its normal engine control operation when the ignition switch of a vehicle is turned off, the control unit can be supplied automatically with operating power to start up and execute an evaporation gas purging diagnosis process for detecting the leakage in the evaporation gas purge system of the vehicle. The distributing mechanism is operable to variably distribute a driving force from an engine to individual drive wheels of a vehicle. When such concave part is formed, the values of the surface area per volume of the intersecting part and the surface area per volume of the first barrier wall before baking and the second barrier wall before baking between the intersecting part and the intersecting part adjacent to the intersecting part become substantially equal. The second link differs from the other links. A carrier body has an inner diameter surface. Entries of the write log may be drained to respective originally intended destinations upon an occurrence of one of a number of conditions.