THE JUDGING METHOD FOR CATALYST BREAKDOWN

摘要

PURPOSE: A catalyst failure determining method is provided to exclude that the output integrated value is set as a factor for determining catalyst failure, thereby efficiently preventing the determination of catalyst failure error despite the state that the catalyst condition is actually not degraded. CONSTITUTION: A catalyst failure determining method comprises the following steps. A catalyst calculates an output integrated value for the corresponding count period by integrating the difference between the output value of catalyst rear sensor and the output average values for the output value. The output integrated value is determined as the factor for determining the catalyst failure based on the result comparing the output integrated value and the preset integration average value. A proportion diagnostic value corresponding to the corresponding count period is calculated if the output integrated value is determined as the factor. The first calculating step or the second calculating step is repeatedly performed as much as the predetermined limit count by increasing the count period. The final catalyst failure determined diagnostic value is calculated by dividing the total amount of proportion diagnostic value for the count period into the limit count. The normal catalyst or the failure catalyst is determined based on the result comparing the predetermined threshold with the final catalyst failure determining diagnostic value. [Reference numerals] (100) Catalyst monitoring device; (AA) Air cleaner box; (BB) Throttle body; (CC) Fuel tank; (DD) Catalyst converter; (EE) Engine