| 摘要 |
<p>PURPOSE: To enable detection of the state of discharge failure and supply capacity lowering in secondary air by setting a diagnostic area within the specified exhaust-pressure range centered on a point that is somewhat less than the shutoff exhaust pressure, and in the case where a driving state is accorded with this diagnostic area, discharging the secondary air from a secondary air supplying means. CONSTITUTION: On the basis of a voltage value of an air pump 21, a diagnostic area is set up in referring to a flow map being situated at this side as far as the specified pressure from each shutoff exhaust pressure and set up with the specified width. Driving conditions of an engine such as engine speed and load are read, and whether they are accorded with the diagnostic conditions or not is judged. When it is YES, drive of the air pump 21 is checked, an air-fuel ratio in exhaust is read out of an air-fuel ratio sensor 16. After the elapse of the specified time, the air-fuel ratio in the exhaust is read out of the air-fuel ratio sensor 16, comparing it with the initial value, and a portion of alteration in the air-fuel ratio is calculated, and a fact that whether it goes beyond the present specified value or not is judged. If secondary air is supplied normally, it is judged to be YES, but when this secondary air is not suppliable due to defective in the air pump 21 and an air cut valve 22, it is so judged as being NO.</p> |
