Patent ID: 6807806
Filing Date: 2004-10-26
Classification: F01N,F02D,Y02T

Abstract:
Diagnostic system for an engine exhaust gas purifying apparatus having a catalyst, said diagnostic system comprising the steps of:providing a first air-fuel-ratio sensor which detects an air-fuel ratio of the exhaust gas upstream of said catalyst, and a second air-fuel ratio sensor which detects an air-fuel ratio of the exhaust gas downstream of said catalyst; calculating a catalyst-deterioration-index calculation indicative of a deterioration state of said catalyst from output signals of said first air-fuel ratio sensor and said second air-fuel-ratio sensor; deciding the deterioration state of said catalyst through a comparison between a predetermined threshold value and the catalyst deterioration index; and stopping catalyst-deterioration-diagnosis when a continuous misfire occurs in at least one specific cylinder in said engine.