Internal combustion engine exhaust system catalytic converter condition diagnosis uses rich and lean exhaust gas feeds and signals from probe downstream of converter

摘要

The condition diagnosis procedure for an exhaust system catalytic converter (28, 29) with a nitrogen and oxygen storage capacity that is modified over time, consists of adjusting the converter's pre-defined regeneration state by feeding it with a rich exhaust gas for a first time period, followed by a lean gas for a second time period, during which the excess oxygen level is increased. The condition diagnosis procedure for an exhaust system catalytic converter (28, 29) with a nitrogen and oxygen storage capacity that is modified over time, consists of adjusting the converter's pre-defined regeneration state by feeding it with a rich exhaust gas for a first time period, followed by a lean gas for a second time period, during which the excess oxygen level is increased. The resulting signal from a probe (36) located downstream of the converter is then evaluated to determine the converter's oxygen storage capacity. The second time period is determined by the time taken for a first lambda value upstream of the converter and a second lambda value downstream of it to be reached.