Patent ID: 7895830

Claim:
An exhaust gas purification system for an internal combustion engine, comprising: a filter that is disposed in an exhaust passage and that traps particulate matter discharged from the internal combustion engine; a differential pressure sensor that detects a differential pressure between a portion of the exhaust passage upstream of the filter and a portion of the exhaust passage downstream of the filter; an exhaust throttle valve that is disposed downstream of the filter in the exhaust passage and that adjusts a cross sectional area of the exhaust passage and is operated based upon the differential pressure detected by the differential pressure sensor thereby the particulate matter trapped by the filter is burned so that the filter is regenerated; and a determining section that determines whether the exhaust throttle valve is malfunctioning based upon a change in the differential pressure that is detected by the differential pressure sensor when the exhaust throttle valve is operated, and determines whether the exhaust throttle valve is malfunctioning based on the change in the differential pressure and an amount of accumulated particulate matter.