| 摘要 |
<p>PURPOSE: To provide a catalyst diagnose by detecting diagnostic parameters in a predetermined region of a diagnostic operation wherein the region is changed based on an outside air temperature so as to diagnose catalyst deterioration accurately even if the outside air temperature becomes lower. CONSTITUTION: If first and second oxygen sensors 16, 17 are in a normal and active state under an air-fuel ratio feed back control and a water temperature is higher than a predetermined temperature, an intake air temperature detected by an intake air temperature sensor 18 is read as an equivalent amount of an outside air temperature. It is judged whether an outside air temperature is lower than a predetermined temperature or not. If the outside air temperature is judged higher than the predetermined temperature, a diagnostic operation region previously designed as an operation region within a normal operation region is set as an operation region for diagnozing catalyst deterioration. If the outside air temperature is judged lower, a diagnostic operation region for lower outside air temperature previously designed for operating under a high loading and high revolution condition is set as an operation region for diagnosing catalyst deterioration, wherein catalytic converter rhodium 10 is heat up to an active temperature by receiving exhaust air.</p> |
