Patent ID: 8280575

Claim:
An abnormality diagnosis system for diagnosing abnormality of an internal combustion engine, which has an actuator operable to control a controlled variable of an object to be controlled to a target value, when fuel is converted to rotational energy, the abnormality diagnosis system comprising: means for changing the target value forcibly; and determination means for determining presence or absence of an abnormality in a response characteristic of the actuator by checking, under a condition that a target value of either one of the operating quantity and the controlled variable is changed, whether a maximum value of a time differential value of a detection value of either one of the operation quantity of the actuator and the controlled variable of the object is within a predetermined normal range defined by an upper limit and a lower limit of the maximum value or whether a minimum value of the time differential value is within a predetermined normal range defined by an upper limit and a lower limit of the minimum value.