Method and apparatus for managing flow through an exhaust aftertreatment system

A system, comprising:

• an internal combustion engine fluidly coupled via an exhaust pipe to an exhaust purifying system, wherein the exhaust purifying system includes a first purifying device fluidly coupled to a second purifying device;
• an exhaust gas sensor disposed in the exhaust pipe upstream of the first purifying device to monitor an exhaust gas feedstream;
• at least one diverter valve disposed to manage the exhaust gas feedstream in the exhaust purifying system;
• the at least one diverter valve fluidly coupled to an exhaust diversion pipe;
• a controller, operatively connected to the internal combustion engine, the exhaust gas sensor and the diverter valve, the controller including an instruction set that is executable to:
• detect operation of the engine in a Deceleration Fuel Cut-Off (DFCO) state;
• monitor, via the exhaust gas sensor, air/fuel ratio of the exhaust gas feedstream via the exhaust sensor;
• control the at least one diverter valve to divert the exhaust gas feedstream through the exhaust diversion pipe away from at least one of the first and second purifying devices during the DFCO event when the exhaust gas feedstream has an air/fuel ratio that is greater than a threshold air/fuel ratio.