PURPOSE: To widely detect abnormality such as the reduction of a power supply voltage digitally comparing a power supply voltage detecting input with the minimum operation voltage of an integrated circuit constituting a control device to detect the abnormality of the detecting input.
CONSTITUTION: The A/D converted data of the power supply voltage detecting input V0 are compared with data corresponding to the minimum operation voltage of the integrated circuit constituting the engine control device 7 to detect abnormality. Namely, the drop of the power supply voltage of the battery or a circuit failure from a power supply up to an A/D converter 5 causes the converted data to be reduced less than the data corresponding to the minimum operation voltage of the integrated circuit. Thus, the abnormality detecting device capable of detecting the abnormality of the power supply voltage detecting input can be obtained.