| 摘要 |
<p>PURPOSE:To accurately detect deterioration of a catalyst by providing a phase difference detection means which detects phase difference between output signal of upstream oxygen sensors, an average value detection means which detects an average value of the phase differences during a specified time, and a judging means which judges that the catalyst is under a deteriorated condition, when the average value is at the specified value or less. CONSTITUTION:An engine control means is arranged upstream from a catalyst to be arranged in the exhaust system of an engine for purifying exhaust gas so that meanwhile phase differences between the output signals of the upstream and downstream oxygen sensors are detected by a phase difference detection means, and the average value of the phase difference during the specified time is detected by an average value detection means. When the average value is judged to be less than the average value by the judging means, it is judged that the catalyst has been deteriorated.</p> |
