Patent ID: 8769928

Claim:
An exhaust system for a combustion engine, comprising: an exhaust passage; a reduction catalyst disposed within the exhaust passage; an injection device configured to inject reductant into the exhaust passage upstream of the reduction catalyst, the reductant selected to facilitate within the reduction catalyst a reduction of an exhaust constituent; a sensor configured to generate a signal indicative of a concentration of the exhaust constituent and the reductant within the exhaust passage; and a controller in communication with the sensor and the injection device, the controller being configured to: calculate a value indicative of a rate of change of the signal for a period of time as a cumulative sum of time weighted based on an absolute value of the rate of change of the signal and a flow rate of exhaust through the reduction catalyst; make a comparison of the value indicative of the rate of change of the signal for the period of time with a threshold amount; make a determination of whether the sensor is sensing a concentration of the exhaust constituent or the reductant based on the comparison; and adjust operation of the injection device based on the determination.