| 摘要 |
PURPOSE:To prevent wrong detection of abnormality of air-fuel ration by performing abnormality detection of air-fuel ratio on condition that the air-fuel ratio is certainly rich. CONSTITUTION:After judgment is made as to whether or not an internal combustion engine is being placed under lean burn control, detection of abnormality of air-fuel ratio is performed on condition the air-fuel ratio is certainly rich. To be more precise, when the value of correction for decrease in quantity is zero (P1), and the value of correction for increase in quantity is not zero (P2), and further an output signal of air-fuel ratio sensor is lean (P3), air-fuel ratio is judged to be abnormal (P4). The value of correction for increase and decrease in quantity means the quantity of correction in case of correcting the basic fuel quantity through stopping feedback control at the time of urgent acceleration, high load or the like. Thus, wrong detection of abnormality of an air-fuel sensor is prevented. |
