Patent ID: 7111451

Claim:
A process for controlling an exhaust system for an internal combustion engine, comprising: flowing exhaust gas from the engine past a first oxygen sensor, through a NOx adsorber, past a second oxygen sensor, through a catalyst and past a third oxygen sensor, wherein the first oxygen sensor, the second oxygen sensor, and the third oxygen sensor, are in operable communication with an electronic control module; using a switching delay between the first oxygen sensor and the second oxygen sensor to determine a NO x value, wherein the NO x value is selected from the group consisting of a NO x regeneration time, a stored NO x amount, a NO x storage efficiency, and combinations comprising at least one of the foregoing NO x values; and initiating a desulfurization process when the NO x value is less than or equal to a first selected value, wherein the desulfurization process comprises increasing a temperature in the exhaust gas to a desulfurization temperature; switching the engine operation from a normal combustion condition to a rich combustion condition to produce a rich exhaust gas; monitoring the rich exhaust gas exiting the catalyst; and providing oxygen to the catalyst when, during the desulfurization process, the third oxygen sensor signals a third condition rich of stoichiometry.