MALFUNCTION DIAGNOSIS DEVICE FOR CRANK-ANGLE SENSOR, AND MALFUNCTION DIAGNOSIS METHOD FOR CRANK-ANGLE SENSOR

A malfunction diagnosis device for a crank-angle sensor (42) that outputs, during rotation of a crankshaft (31), a pulse signal in a mode varying depending on a rotational direction of the crankshaft, includes an electronic control unit (41) configured: to determine that the crank-angle sensor is malfunctioning upon satisfaction of a malfunction determination condition including a first condition that an engine speed at change timing, at which the mode of the pulse signal changes from a first mode corresponding to forward rotation of the crankshaft to a second mode corresponding to reverse rotation thereof, is higher than or equal to a determination value lower than an idling speed, and a second condition that the engine speed continues to be higher than or equal to the determination value from the change timing; and not to make a determination that the crank-angle sensor is malfunctioning when the malfunction determination condition is not satisfied.