Patent ID: 7059112

Claim:
An emission control system for an internal combustion engine, comprising: a NOx absorbent disposed in an exhaust passage of the internal combustion engine that stores and reacts NOx under certain operating conditions; a NOx sensor disposed in the exhaust passage downstream of the NOx absorbent, an output of the NOx sensor corresponding to a NOx concentration of exhaust gas flowing out of the NOx absorbent; a controller calculating an operating condition of the internal combustion engine and determining a deviation of the output value of the NOx sensor from a predetermined value when preselected engine operating conditions are met; an air-fuel ratio sensor disposed in the engine exhaust passage; and said controller further indicating whether predetermined engine operating conditions are present, and in response to said determination, adjusting a fuel injection amount into the internal combustion engine based on said air-fuel ratio sensor, wherein said controller further adjusts said fuel injection amount into the internal combustion engine independent of said air-fuel ratio sensor when said controller indicates said predetermined engine operating conditions are not present.