Method for diagnosing selective catalytic reduction-catalyst system for reducing nitrogen oxides in exhaust gas of e.g. diesel engine of motor car, involves determining aging state of catalyzer from difference between sensor signals

摘要

The method involves detecting a sensor signal (S44) of a sensor with sensitivity opposite nitrogen oxides and ammonia in an exhaust line between two selective catalytic reduction-catalyzers. Another sensor signal (S46) of another sensor is detected with oxides and ammonia in the line downstream of one of the catalyzers. Aging state of the catalyzer is determined from a difference between the sensor signals or a value that is derived from the former sensor signal and value derived from another sensor signal during emptying of the catalyzers. Independent claims are also included for the following: (1) a computer program comprising a set of instructions for a method for diagnosing a selective catalytic reduction-catalyst system with selective catalytic reduction-catalyzer in an exhaust line (2) a computer program product with program code, which is stored on a machine-readable carrier comprising a set of instructions for a method for diagnosing a selective catalytic reduction-catalyst system with selective catalytic reduction-catalyzer in an exhaust line.