| 摘要 |
<p>PURPOSE:To accurately perform diagnosis judgement of a secondary air supply device by detecting an output of an oxygen concentration sensor when supply to the secondary air is stopped based on a detection result of a secondary air quantity detection means. CONSTITUTION:Under a condition where a port air supply range in which secondary air is supplied to an exhaust port 2 via a port air supply passage 6 is detected, a control unit 19 stops the operation of a changeover valve 9. In the case an output of an oxygen sensor 20 is not maintained for a specified time, abnormality of the changeover valve 9 is judged. Under a condition where a port leaking range in which the secondary air is supplied to a secondary catalyst converter 5 via a split air supply passage 7 is detected, a control unit 19 stops the operation of an air cut valve 12. In the case where the outputs of oxygen sensors 20-22 are not reversed, abnormality of a port leaking valve 14 or a split valve 16 is judged. Diagnosis judgement of a secondary air supply device is accurately performed thereby.</p> |
