Patent ID: 7680587

Claim:
A monitoring arrangement for monitoring the functioning of a sensor arranged to measure the magnitude of a parameter related to exhaust gases flowing out of an exhaust gas aftertreatment appliance, included in an exhaust gas aftertreatment system of a motor vehicle, wherein the monitoring arrangement comprises calculation apparatus operable for calculating the magnitude of said parameter on the basis of a calculation model; and processor arranged and operable to receive information from the sensor as to the measured magnitude of the parameter and information from the calculation apparatus as to the calculated magnitude of the parameter, the processor being operable a) to establish a first comparison value (C 1 ) based on the information from the sensor as to the measured magnitude of the parameter, b) to establish a second comparison value (C 2 ) corresponding to the first comparison value (C 1 ) based on the information from the calculation apparatus as to the calculated magnitude of the parameter, c) to establish a difference value (V diff ) representing the difference between said comparison values (C 1 , C 2 ), d) to repeat steps a)-c) during a period of time and establish a variance value (V var ) representing the variance of the difference value (V diff ) during this period of time, and e) to compare the variance value (V var ) with a given threshold value (V th ) and generate information regarding the functioning of the sensor.