| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an air fuel ratio control device for an internal combustion engine capable of accurately determining deterioration of a catalyst. <P>SOLUTION: This device is provided with a fuel cut condition detection means detecting a fuel cut state in which supply of fuel to the internal combustion engine is stopped, and a catalyst deterioration determination means determining deterioration of the catalyst based on a period from detection of release of the fuel cut state by the fuel cut state detection means till coincidence of output value of a second air fuel ratio sensor with predetermined return determination value near a target value, and operation quantity of the average air fuel ratio at an upstream side by a second air fuel ratio feed back control means. <P>COPYRIGHT: (C)2009,JPO&INPIT |
