| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an air fuel ratio control device of an internal combustion engine which can accurately monitor a change of an engine operation state after a start of a failure determination in an air fuel ratio control system and can improve accuracy of the failure determination. <P>SOLUTION: A frequency f1 component and a frequency f2 component included in a detection equivalent ratio KACT calculated from an output signal of a LAF sensor 15 in a failure determination period are extracted. Based on the frequency components, it is determined whether a response characteristic deterioration failure occurs in the LAF sensor 15. After start of the failure determination, a change amount integrated value IDXOP is calculated which indicates a fluctuation in a specific operation state parameter XOP and to which a fluctuation history of the specific operation state parameter XOP is reflected. If the change amount integrated value IDXOP is equal to or more than a prescribed threshold IDXOPTH, the failure determination is suspended (stopped). <P>COPYRIGHT: (C)2013,JPO&INPIT |
