| 摘要 |
PURPOSE:To prevent the erroneous judgement by judging anomaly on the basis of the output of an O2 sensor when the air-fuel ratio feedback control conditions are satisfied and each of the cooling water temperature, intake air quantity, and the rich side limit value of the air-fuel ratio correction value becomes over each prescribed value. CONSTITUTION:Each detection value of an air flow meter 3, crank angle sensors 5 and 6, water temperature sensor 9, and an O2 sensor 13, etc. is input into a control circuit 10. The control circuit 10 checks if the air-fuel ratio closed loop control conditions are established or not except on start, in the fuel quantity increase in warming, output increase, and fuel cut. When the air-fuel ratio closed loop control conditions are established, and each of the cooling water temperature and the intake air quantity is over each prescribed value, it is checked if the rich side limit value of the air-fuel ratio correction value is over a prescribed value or not. When it is confirmed that the rich side limit value is over the prescribed value and the engine is in the stationary operation state, judgement for anomaly is performed by observing the output of the O2 sensor.
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