| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve precision of failure diagnosis of a secondary air supplying device for supplying secondary air to a catalyst. SOLUTION: In this self-diagnostic device in a secondary air supplying device of an internal combustion engine, when the secondary air supplying device is operated (S1, S2) in low-temperature start-up, the increase amount correction factor TFBY of the fuel injection amount is lowered (S4) to a minimum value MIN, and diagnosis is started (S7) in a state (S6) in which an oxygen sensor is activated. During diagnosis, the increase amount correction factor TFBYA is held (S5) to the minimum value MIN. When the output of the oxygen sensor provided on the downstream side from a supplying port for secondary air indicates the lean state (S8), the normal judgement of the secondary air supplying device is performed (S9), while, when the oxygen sensor output indicates the rich state (S8), the failure judgement of the secondary air supplying device is performed (S10).</p> |
