Diagnostic methods for a high efficiency exhaust aftertreatment system

A method comprising:

• acquiring, by a processing circuit, nitrogen oxide (NOx) data indicative of a first amount of NOx in an exhaust flow exiting an engine and a second amount of NOx in the exhaust flow exiting an exhaust aftertreatment system coupled to the engine, the exhaust aftertreatment system including a catalyst;
• determining, by the processing circuit, a NOx conversion efficiency fault is present within the exhaust aftertreatment system based on the first amount of NOx and the second amount of NOx;
• monitoring, by the processing circuit, an actual amount of NOx in the exhaust flow downstream of the catalyst;
• determining, by the processing circuit, an expected amount of NOx downstream of the catalyst;
• and
• determining, by the processing circuit, the catalyst is responsible for the NOx conversion efficiency fault in response to the actual amount of NOx differing from the expected amount of NOx by more than a threshold amount.

A system comprising:

• an exhaust aftertreatment system configured to receive an exhaust flow from an engine, the exhaust aftertreatment system including a catalyst;
• and
• a controller structured to:
• acquire nitrogen oxide (NOx) data indicative of a first amount of NOx in the exhaust flow exiting the engine and a second amount of NOx in the exhaust flow exiting the exhaust aftertreatment system;
• determine a NOx conversion efficiency fault is present within the exhaust aftertreatment system based on the first amount of NOx and the second amount of NOx;
• monitor an actual amount of NOx in the exhaust flow downstream of the catalyst;
• determine an expected amount of NOx downstream of the catalyst;
• and
• determine the catalyst is responsible for the NOx conversion efficiency fault in response to the actual amount of NOx differing from the expected amount of NOx by more than a threshold amount.