Method for desulfating an NOx absorber in internal combustion engine

In a process to remove sulfur from an automotive NOx storage trap operated in lean burn mode, a calculation model determines the sulfur removal steps. The steps are modified using information derived from a knock signal and the fuel anti-knock sensitivity, fuel consumption. The fuel consumption is determined during a lean burn phase of motor operation. The fuel consumption is determined since the previous sulfur removal cycle. A relationship is established between the knock-sensitivity and the fuel sulfur concentration. The relationship between knock-sensitivity and sulfur concentration is held in a memory device. A correctional parameter is determined using the knock-sensitivity and fuel consumption. This parameter is incorporated in the calculation model and is determines the sulfur removal process intervals.