PURPOSE: To exactly control an engine when a crankshaft angle sensor is in abnormal condition, by using a signal from an intake pulsation detector instead of that from the crankshaft angle sensor found in abnormal condition by a crankshaft angle sensor signal abnormality detector, to regulate a control equipment.

CONSTITUTION: To detect whether a crankshaft angle sensor 1 is in abnormal condition or not, the rotational number of an engine is calculated from a 1° signal and then from a 180° signal. If both the rotational number values calculated from these signals have a difference of 20% or more, the sensor 1 is judged to be in abnormal condition. Supposing the engine has four cylinders, two intakes are performed during one rotation of the crankshaft of the engine or there are two intake pulsations during one rotation. The period T of the intake pulsation is detected to calculate the rotational number of the engine through the output signal of an air flow meter 14. Since the maximum value of the output voltage of the air flow meter 14 corresponds to the end of the intake process of the cylinder during the period T immediately before the maximum value of the output voltage, the angle of the crankshaft can be determined by calculating the angles at which a power transistor 21 is turned off and on after the maximum value of the output voltage of the air flow meter. Control is performed on the basis of both the determined angles.