Degradation detection method for an engine having a NOx sensor

摘要

An engine diagnostic system for use with an internal combustion engine coupled to a lean NOx trap with a NOx sensor coupled downstream of the trap. Degradation of the NOx sensor is determined by estimated NOx exiting the trap based on engine out NOx and various other operating conditions. When the difference between the measured NOx and estimated NOx is greater than a predetermined value for a predetermined duration, degradation is indicated.