Exhaust aftertreatment subsystem

A system for monitoring an oxidation catalyst arranged in an exhaust gas feedstream of a compression-ignition internal combustion engine, comprising:

• a first NOx sensor arranged to monitor the exhaust gas feedstream upstream of the oxidation catalyst;
• a second NOx sensor arranged to monitor the exhaust gas feedstream downstream of the oxidation catalyst;
• a controller, in communication with the first and second NOx sensors;
• the controller including an instruction set, the instruction set including:
• a first relationship for the first and second NOx sensors corresponding to nitrogen oxide (NOx);
• a second relationship for the first and second NOx sensors corresponding to nitrogen dioxide (NO2);
• wherein the instruction set is executable to:
• determine, via the first NOx sensor, a first NOx parameter;
• determine, via the second NOx sensor, a second NOx parameter;
• determine an NO2 parameter based upon the first NOx parameter, the second NOx parameter, the first relationship for the first and second NOx sensors, and the second relationship for the first and second NOx sensors;
• evaluate NO2 production of the oxidation catalyst based upon the NO2 parameter;
• and
• communicate the evaluating of the NO2 production of the oxidation catalyst to a second controller wherein the instruction set being executable to determine the NO2 parameter based upon the first NOx parameter, the second NOx parameter, the first relationship for the first and second NOx sensors, and the second relationship for the first and second NOx sensors comprises the instruction set being executable to determine NO2 production by the oxidation catalyst based upon the following relationship:
• NO2DOC=(1+(SlopeFTIR/SlopeNOxNO2))*(NOxs1−NOxs2)
• wherein:
• NO2DOC represents the NO2 production by the oxidation catalyst;
• SlopeFTIR represents the first relationship for the first and second NOx sensors;
• SlopeNOxNO2 represents the second relationship for the first and second NOx sensors;
• NOxs1 represents the first NOx parameter;
• and
• NOxs2 represents the second NOx parameter.

A system for monitoring an oxidation catalyst for a lean-burn internal combustion engine, comprising:

• a first NOx sensor arranged to monitor an exhaust gas feedstream upstream of the oxidation catalyst;
• a second NOx sensor arranged to monitor the exhaust gas feedstream downstream of the oxidation catalyst;
• a controller, in communication with the first and second NOx sensors;
• the controller including an instruction set, the instruction set including:
• a first relationship for the first and second NOx sensors corresponding to nitrogen oxide (NOx);
• and
• a second relationship for the first and second NOx sensors corresponding to nitrogen dioxide (NO2);
• wherein the instruction set is executable to:
• determine, via the first NOx sensor, a first NOx parameter;
• determine, via the second NOx sensor, a second NOx parameter;
• determine an NO2 parameter based upon the first NOx parameter, the second NOx parameter, the first relationship for the first and second NOx sensors, and the second relationship for the first and second NOx sensors;
• determine NO2 production by the oxidation catalyst based upon the NO2 parameter;
• and
• detect a fault in the oxidation catalyst based upon the NO2 production wherein the instruction set being executable to determine the NO2 parameter based upon the first NOx parameter, the second NOx parameter, the first relationship for the first and second NOx sensors, and the second relationship for the first and second NOx sensors comprises the instruction set being executable to determine NO2 production by the oxidation catalyst based upon the following relationship:
• NO2DOC=(1+(SlopeFTIR/SlopeNOxNO2))*(NOxs1−NOxs2)
• wherein:
• NO2DOC represents the NO2 production by the oxidation catalyst;
• SlopeFTIR represents the first relationship for the first and second NOx sensors;
• SlopeNOxNO2 represents the second relationship for the first and second NOx sensors;
• NOxs1 represents the first NOx parameter;
• and
• NOxs2 represents the second NOx parameter.