System and method for detecting a failed nitrogen oxide sensor

A method for detecting a failure state of a nitrogen oxide (NOx) sensor in a diesel engine, the method comprising:

• ceasing to inject ammonia from an ammonia source to a selective catalytic reduction (SCR) system;
• depleting a remaining ammonia in the SCR system via an exothermic reaction within a regeneration device so as to increase a NOx gas output downstream of the SCR system;
• sensing the increased NOx gas output via a NOx sensor positioned at an outlet the output of the SCR system;
• transmitting one or more NOx gas output readings from the NOx sensor to an electronic control module of the engine;
• comparing the one or more NOx gas output an expected NOx gas output based on engine operating conditions via the electronic control module;
• determining the NOx sensor is in the failure state when the one or more NOx gas output readings deviate from the expected NOx gas output by a predetermined threshold amount;
• and
• optimizing engine operation when the NOx sensor is determined to be in the failure state.

A system for detecting a failure state of a nitrogen oxide (NOx) sensor in an engine, the system comprising:

• a selective catalytic reduction (SCR) system;
• an ammonia source configured to inject ammonia into the SCR system;
• a regeneration device configured to deplete ammonia in the SCR system;
• a NOx sensor positioned at an outlet of the SCR system;
• and
• an electronic control module in communication with the engine, the ammonia source, the regeneration device, and the NOx sensor, the electronic control module configured to:
• instruct the ammonia source to cease injecting ammonia into the SCR system;
• instruct the regeneration device to deplete ammonia remaining in the SCR system so as to increase a NOx gas output downstream of the SCR system;
• receive one more NOx sensor signals from the NOx sensor indicative of the increased NOx gas output;
• compare the one more NOx sensor signals to an expected NOx gas output based on engine operating conditions;
• determine the NOx sensor is in the failure state when the one or more NOx sensor signals deviate from the expected NOx gas output by a predetermined threshold amount;
• and
• optimize engine operation when the NOx sensor is determined to be in the failure state.