| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust gas sensor diagnostic device diagnosing a lowering degree of responsiveness of an exhaust gas sensor. SOLUTION: An oxygen concentration in an exhaust passage rises and converges at an equivalent to the atmosphere when being put in a fuel-cut state by turning-off of an accelerator. In the transition state, the diagnostic device estimates normal output 320 of an A/F sensor normal in responsiveness and deteriorated output 324 when the responsiveness is deteriorated by a predetermined value relative to the normal output 320, and detects actual output 322 in a real state of the A/F sensor. While the normal output 320 and the lowered output 324 converge at an oxygen concentration equivalent to the atmosphere, the diagnostic device respectively calculates an integrated value S1 of differences between the normal output 320 and the deteriorated output 324 and an integrated value S2 of differences between the normal output 320 and the actual output 324. S2 varies according to a lowering degree of responsiveness of the actual output 322 and therefor the lowering degree of responsiveness of the A/F sensor can be diagnosed based on S1/S2. COPYRIGHT: (C)2011,JPO&INPIT
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