comprises a nox adsorber catalyst 35 that adsorbs nox in the exhaust flow to limit the amount that passes through to the ambient surroundings catalyst 35 periodically requires regeneration regeneration involves removal of the adsorbed nox and this can be accomplished by increasing the concentration of carbon monoxide co passing through the catalyst regeneration is initiated by an operating program that is resident in control 30 data used in the disclosed example of operating program includes the concentration of nox in the exhaust after passing through catalyst 35 that data is obtained from a nox sensor 31 that is typically a standard component of the engine system when catalyst 35 is present an exhaust temperature sensor 33 may also provide temperature data for processing engine 10 further comprises a kinematic mechanism including pistons 32 that reciprocate within cylinders 16 and are coupled by rods 34 to a crankshaft 36 when running the engine executes the usual 720 u00b0 engine cycle comprising intake compression power and exhaust strokes each of the four strokes being of 180 u00b0 duration intake and power strokes occur on downstrokes of pistons 32 while compression and exhaust strokes occur on upstrokes as injected fuel is combusted in cylinders 16 during each engine cycle the energy of combustion is converted to crankshaft output torque to run the engine and operate the motor vehicle engine control 30 contains a software operating program that implements the one or more algorithms used for control of engine operation including control of timing of valves 18 and 24 via mechanism 26 and fueling of cylinders 16 via fuel injectors 20.