US 6,981,368 B2
Exhaust gas aftertreatment systems
Michiel J. van Nieuwstadt, Ann Arbor, Mich. (US); and Devesh Upadhyay, Dearborn, Mich. (US)
Assigned to Ford Global Technologies, LLC, Dearborn, Mich. (US)
Filed on Nov. 21, 2002, as Appl. No. 10/301,387.
Prior Publication US 2004/0098968 A1, May 27, 2004
Int. Cl. F01N 3/00 (2006.01)
U.S. Cl. 60—277 18 Claims
OG exemplary drawing
 
1. A method for diagnosing an exhaust gas aftertreatment device coupled downstream of an internal combustion engine, comprising:
calculating a difference between a measured and an estimated amount of an exhaust gas component downstream of the device; and
providing an indication of device degradation based on a length of time a magnitude of said difference remains greater than a predetermined constant.