Abstract: A method for determining a condition of a catalyst disposed in an exhaust of an engine. The method includes sensing a common property of both the exhaust upstream and downstream of the catalyst; taking samples of such upstream and downstream sensed property over a period of time; accumulating the samples over the period of time; determining statistical characteristics of the sensed common property of the upstream and downstream common property; comparing the determined statistical characteristics of the sensed upstream property with the determined statistical characteristics of the downstream property to determine whether catalyst was in a proper operating condition during such period of time. With such method statistical characteristics are determined from samples as they are obtained and then once obtained, processed to determine the condition of the catalyst. Such method thereby reduces memory or data storage requirements and also reduces computational requirements.

Abstract: A system and method for monitoring a conditioning catalyst positioned upstream of an oxygen sensor used for feedback control of an internal combustion engine include comparing shapes of an upstream oxygen sensor signal and of the signal from the oxygen sensor used for feedback control of the engine while ignoring the signal amplitudes and mean values. Operational efficiency of the conditioning catalyst is determined based on a measure of the relative similarity or difference between the two signals.