Method and apparatus for detecting abnormality of nitrogen oxide purifying catalyst

摘要

A method and apparatus for detecting an abnormality of a nitrogen oxide purifying catalyst using an NOx sensor, the method including: calculating a detection integrated value by integrating corresponding values corresponding to the NOx sensor output signal obtained until a first predetermined detection period has elapsed after the NOx sensor begins to generate an output signal and subtracting a variation integrated value. The variation integrated value is calculated by integrating corresponding values obtained until a predetermined second detection period has elapsed after the NOx sensor beings to generate an output signal when driven in a gas atmosphere having a constant nitrogen oxide concentration.