Abstract: A method of diagnosing deterioration of an exhaust emission control catalyst is provided. The catalyst includes an HC (hydrocarbon) adsorbing part and an oxidation catalyst part. The method includes estimating that an HC discharge amount discharged from the HC adsorbing part is larger than a first value, detecting a parameter relating to a reaction heat of the exhaust emission control catalyst, and diagnosing that the exhaust emission control catalyst is deteriorated when the detected parameter indicates a temperature value lower than a predetermined threshold. The deterioration diagnosis is performed under a first condition that the HC discharge amount is estimated to be larger than the first value.

Abstract: A method of diagnosing deterioration of an exhaust emission control catalyst is provided. The catalyst includes an HC (hydrocarbon) adsorbing part and an oxidation catalyst part. The method includes estimating that an HC discharge amount discharged from the HC adsorbing part is larger than a first value, detecting a parameter relating to a reaction heat of the exhaust emission control catalyst, and diagnosing that the exhaust emission control catalyst is deteriorated when the detected parameter indicates a temperature value lower than a predetermined threshold. The deterioration diagnosis is performed under a first condition that the HC discharge amount is estimated to be larger than the first value.

Abstract: A deterioration diagnosing system for an exhaust emission control catalyst of an engine is provided. The catalyst includes an HC adsorbing part and an oxidation catalyst part. The system includes an actual exhaust-emission-control-catalyst temperature parameter detecting module for detecting a parameter correlating with an actual exhaust-emission-control-catalyst temperature. The catalyst also includes a deterioration determining module for receiving a detection value from the actual exhaust-emission-control-catalyst temperature parameter detecting module when predetermined diagnosis executing conditions are met, and determining that the exhaust emission control catalyst is deteriorated when the detection value is smaller than a predetermined diagnostic temperature parameter threshold. The catalyst also includes an HC discharge amount calculating module for calculating an amount of discharging HC from the HC adsorbing part.