PURPOSE: To create a method and device which turns off or inverts the driving device of the movable member of an automobile and is useful for preventing malfunction more excellently.

CONSTITUTION: During diagnosis operation useful for the diagnosis of measuring paths 19 and 22, a known input signal is applied to the input of a measurement path, an actual output signal appearing at a measurement path output based on a known input signal is compared with a specific target output signal which is predicted at the measurement path output when the measurement path operates properly, and then the output signal appearing at the measurement path output during working operation is corrected or the driving device is switched to a trouble operation.