Patent ID: 6898927

Claim:
An emission control system, comprising: a catalyst provided on an exhaust passage of an internal combustion engine to be used as a means for purifying exhaust gas discharged by the internal combustion engine; a catalyst warming up speeding control means for speeding an operation to warm up the catalyst; a diagnosis means for making a diagnosis of the catalyst warming up speeding control means in order to determine whether the catalyst warming up speeding control means is functioning normally or abnormally; and an exhaust gas component detection means for detecting a component contained in exhaust gas on the downstream side of the catalyst, wherein the diagnosis means comprises: a first diagnosis means for preliminarily detecting an abnormality of the catalyst warming up speeding control means or an abnormality caused by a deteriorating state of the catalyst on the basis of an exhaust gas component detected by the exhaust gas component detection means in the course of control executed by the catalyst warming up speeding control means to speed an operation to warm up the catalyst; and a second diagnosis means for confirming the deteriorating state of the catalyst on the basis of an exhaust gas component detected by the exhaust gas component detection means after completion of the control to speed an operation to warm up the catalyst, and wherein the diagnosis means makes a diagnosis of the catalyst warming up speeding control means in order to determine whether or not an abnormality exists in the catalyst warming up speeding control means on the basis of a preliminary detection result output by the first control means and the second control means confirmation result indicating whether or not the deteriorating state of the catalyst is confirmed.