| 摘要 |
PROBLEM TO BE SOLVED: To accurately judge the degradation of an air-fuel ratio sensor even when the fuel property is different. SOLUTION: The fuel injection from a fuel injection valve 4 is controlled based on the output of the air-fuel ratio sensor 11 so as to obtain the target air-fuel ratio to be set based on the operational condition. This degradation diagnostic device comprises a means to judge the fuel property, a means to judge the diagnostic range of the air-fuel ratio sensor 11, a means to judge the degradation of the air-fuel ratio sensor 11 by comparing the output change of the air-fuel ratio sensor 11 with a predetermined reference value in this diagnostic range, and a means to stop the diagnosis of the air-fuel ratio sensor 11 by the fuel property.
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