Method and system for reducing exhaust gases from a vehicle using a located downstream of an exhaust gas sensor control device

The invention relates to a method and system for controlling a lean-burn engine (12), the exhaust gas is passed through an exhaust treatment system (30) having an exhaust control apparatus (34) alternately a selected component of exhaust gas as NO¶x¶, based on engine operating conditions stores and releases and a downstream of the device (34) used NO¶x¶ sensor (40). The system estimates the in the device (34) flowing NO¶x¶ concentration in exhaust gas based on the engine operating conditions, and determines based on the from NO¶x¶ sensor (40) produced output signal has a concentration of (from the device 34 ) flowing NO¶x¶ specified value. A washing result is initiated for the device (34) when the based calculated on the NO¶x¶ concentration values ​​from flowing into the device and out of the device NO¶x¶ efficiency falls below a predetermined minimum efficiency. The length of a purge event is determined as a function of an accumulated amount that is determined from the difference between the NO¶x¶ concentration values ​​in the apparatus (34) and from it effluent NO¶x¶ (Figure 1).