Vehicular electronic control apparatus

A vehicular electronic control apparatus includes a mother unit having a microcomputer, a plurality of ECU modules connected to the mother unit detachably and configured to execute respective vehicle controls, an operation data communication section for communicating with the microcomputer operation data used by the plurality of ECU modules in executing respective control operation processing, and alternative operation execution section for causing at least one of the other ECU modules and the microcomputer to execute, as an alternative operation, at least a part of the arithmetic operation processing, which is to be executed by at least one of the plurality of the ECU modules.