A method (200) to determine a performance characteristic of an exhaust system (14) of an engine (10), where the exhaust system (14) includes an exhaust gas sensor (22) that outputs an exhaust gas signal (28). A combustion event in a cylinder (18a) is fuele...

A measuring unit determines a change time period from the time the output of a downstream oxygen concentration sensor (15) has reached a first predetermined value to the time the output of the sensor reaches a second predetermined value. A determining unit...