| 摘要 |
<p>PURPOSE:To reliably detect an abnormality and prevent the overheat and heat deterioration of a ternary catalyst by judging that a secondary air feeding mechanism is abnormal if the air fuel ratio is kept lean for a fixed period or longer during the augmentation of fuel. CONSTITUTION:When a control circuit 51 judges an engine high-load operation state, it controls to augment the fuel injection quantity than the normal operation state. During the augmentation control, whether the air fuel ratio is lean or not is judged based on the output signal of an O2 sensor 43. If the air fuel ratio is lean, there is a possibility that a secondary air feeding mechanism 44 is abnormal, and a counter is applied with an increment. If the counter attains a preset value or more, it is judged that the secondary air is fed to an exhaust passage 41 and the secondary air feeding mechanism 44 is possibly abnormal, and a warning light 61 is lighted. Accordingly, the overheat and heat deterioration of a catalyst 42 can be prevented when the secondary air feeding mechanism 44 becomes abnormal.</p> |
