Method for controlling of an operating mode of a lean burn internal combustion engine

Process for controlling an operating modulus of a lean burn IC engine (10) having an exhaust gas tract (14) with a NOx storage catalyst (20) and a gas sensor (24) comprises allowing a lean operating modulus of the engine with lambda more than 1 depending on threshold values for a temperature of the catalyst and for a further operating parameter of the engine and/or exhaust gas tract; and varying at least one threshold value depending on an actual NOx storability and/or NOx convertibility of the catalyst. Preferred Features: The further parameter comprises a NOx crude emission of the engine and/or a crude emission of a further exhaust gas component. The further exhaust gas component comprises non-combustible hydrocarbons, carbon dioxide and/or carbon monoxide.