An apparatus for detecting an abnormality in an A/D converter has a voltage accumulating
capacitor. The apparatus includes a storage circuit which receives analog signals
whose range of signal operation voltage when normal is limited to be narrower than
the range of input operation voltages, and stores in advance the range of abnormal
voltages of digital signals converted by the A/D converter, and determines the
A/D converter to be abnormal when the digital signal voltage lies in the range
of abnormal voltages. The A/D converter converts the analog signal voltage into
a digital signal voltage, and then initializes the analog signal voltage of the
capacitor to a voltage in the abnormal voltage range.