| 摘要 |
PROBLEM TO BE SOLVED: To accurately diagnose failure by diagnosing a characteristic change failure of the intake air quantity detecting device, when a detection value of the intake air quantity and a learning value thereof are compared with each other and the predetermined number or more operation area, in which the detection value is changed at a predetermined ratio or more in relation to the learning value. SOLUTION: Each detecting signal of an air flow meter 6, a crank angle sensor 9 and a throttle sensor 11 is taken into a control unit 12, and a learning value L-AFM of the intake air quantity is searched from a map, on the basis of the detected engine speed and the extent of throttle opening. Continuously, a discrimination whether US is changed at the prescribed ratio or more in relation to the L-AFM or not is done. When it is 'YES', operation area of this stage is stored. A number N of the operation area, in which change more than the prescribed ratio is discriminated, is counted up, and when the counted value exceeds the prescribed value, the air flowmeter 6 is diagnosed to have characteristic change failure.
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