DIAGNOSEVERFAHREN ZUR ABGASBEHANDLUNGSSYSTEM MIT SELEKTIVER KATALYTISCHER REDUKTION (SKR)

In an internal combustion engine system having an exhaust aftertreatment system including a selective catalytic reduction (SCR) catalyst (38), diagnostic methods involve the intrusive perturbation of a target surface coverage parameter theta to determine the state of health of the SCR catalyst (38) or an ammonia concentration sensor (60). An adaptive learning block adapts the target theta based on the use of NH 3 sensing feedback from a mid-brick positioned ammonia concentration sensor (60) to pull in system variation. A further diagnostic monitors the amount of adaptation and when the adaptive learning excessively learns, the diagnostic assumes that some system-level degradation must have occurred and the diagnostic will notify the overall emissions control monitor.