Patent ID: 7082752

Claim:
A method of diagnosing an exhaust gas aftertreatment system positioned in an exhaust line of an internal combustion engine, comprising: increasing a proportion of uncombusted hydrocarbons in the exhaust gas of the internal combustion engine by a fuel afterinjection; measuring a first temperature of an exhaust gas upstream from the exhaust gas aftertreatment system by a first temperature sensor; measuring a second temperature of the exhaust gas downstream from the exhaust gas aftertreatment system by a second temperature sensor; providing a diagnosis by recognizing an error-free exhaust gas aftertreatment system if an expected temperature increase of the second temperature measured downstream from the exhaust gas aftertreatment system occurs because of the increase in the proportion of uncombusted hydrocarbons in the exhaust gas of the internal combustion engine; and providing the diagnosis only if the temperature upstream from the exhaust gas aftertreatment system as measured by the first temperature sensor only changes insignificantly within a period of time after the proportion of uncombusted hydrocarbons is increased.