| 摘要 |
PROBLEM TO BE SOLVED: To suppress an emission degradation to the minimum by appropriately determining correction abnormality in air-fuel ratio subfeedback control and by giving a driver a warning. SOLUTION: The correction abnormality in the air-fuel ratio subfeedback control is determined by using at least one index of deviation between output voltage VOX2 relative to oxygen concentration detected by an oxygen sensor 27 and a target voltage, an air-fuel ratio subfeedback corrective amount and an air-fuel ratio subfeedback learning value. Therefore, when variation in respective indices reaches respective determination values exerting an influence on emission, correction in the air-fuel ratio subfeedback control is determined as abnormal. For example, a warning lamp in a meter panel is lighted and correction abnormality can be quickly transmitted to the driver, thereby minimizing the emission degradation to the minimum. COPYRIGHT: (C)2004,JPO&NCIPI
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