System and method for vehicle oxidation catalyst monitoring

A method for use aboard a vehicle having an engine generating an exhaust gas, an exhaust system in fluid communication with the engine including an oxidation catalyst, a particulate filter and a diagnostic control system including a controller and at least one temperature sensor disposed proximate the oxidation catalyst in communication with the controller, the method comprising:

• using the controller to determine an operating state of at least one of the engine and exhaust system,
• initiating a particulate filter regeneration process in response to the detected operating state;
• calculating a ratio of a heat release value to an amount of post injection fuel released in a time period of the particulate filter regeneration process to define a first diagnostic index value;
• determining an offset value based upon temperature of the exhaust gas in the particulate filter regeneration process time period measured with the at least one temperature sensor;
• calculating a ratio of the first diagnostic index value and the offset value to define a second diagnostic index value;
• and
• using an oxidation catalyst efficiency validation module of the controller to evaluate the second diagnostic index value to determine the efficiency of the oxidation catalyst.

A method of assessing efficiency of an oxidation catalyst of an exhaust system including a particulate filter for a vehicle, the method comprising:

• providing a diagnostic control system including a controller and at least one temperature sensor in communication with the controller and disposed proximate the oxidation catalyst;
• initiating a particulate filter regeneration process when the at least one temperature sensor measures exhaust gas temperature at the inlet of the oxidation catalyst between about 200 degrees Celsius and about 350 degrees Celsius;
• calculating a ratio of a heat release value to an amount of post injection fuel released in a time period of the particulate filter regeneration process to define a first diagnostic index value;
• determining an offset value based upon temperature of the exhaust gas in the particulate filter regeneration process time period measured with the at least one temperature sensor;
• calculating a ratio of the first diagnostic index value and the offset value to define a second diagnostic index value;
• and
• evaluating the second diagnostic index value to determine the efficiency of the oxidation catalyst with an oxidation catalyst efficiency validation module of the controller.