A fuel cut failsafe function monitoring section of a microcomputer sets a fuel cut failsafe function diagnosis period in a period, in which an operation of an engine is stopped (e.g., a period before engine start), and sends a fuel cut failsafe execution command signal to a fuel cut failsafe execution section of an abnormality monitoring device during the fuel cut failsafe function diagnosis period. Thus, the fuel cut failsafe execution section is caused to output a fuel cut failsafe signal to an injector driver to stop an operation of the injector driver. The fuel cut failsafe function monitoring section monitors an output level of a disablement port of the injector driver at the time, thereby performing abnormality diagnosis of a fuel cut failsafe function.