NOx SENSOR DIAGNOSTIC FOR AN EXHAUST AFTERTREATMENT SYSTEM

A method, comprising:

• adjusting at least one of an ignition timing and an engine speed for an engine to adjust an engine out nitrogen oxide (NOx) amount;
• interpreting measured SCR inlet NOx data from a SCR inlet NOx sensor and measured SCR outlet NOx data from a SCR outlet NOx sensor;
• determining a phase shift between the measured SCR inlet and outlet NOx data;
• applying the determined phase shift to the SCR outlet NOx data;
• and
• determining a diagnostic feature based on the SCR inlet NOx data and the phase shifted SCR outlet NOx data regarding a state of the SCR inlet and outlet NOx sensors.

A system, comprising:

• a controller configured to:
• adjust a nitrogen oxide (NOx) amount received by a selective catalytic reduction (SCR) system;
• interpret a measured SCR inlet NOx data from a SCR inlet NOx sensor and a measured SCR outlet NOx data from a SCR outlet NOx sensor;
• determine a phase shift between the measured SCR inlet and SCR outlet NOx data;
• apply the determined phase shift to the SCR outlet NOx data;
• and
• determine a diagnostic feature based on the SCR inlet NOx data and the phase shifted SCR outlet NOx data regarding a state of the SCR inlet and outlet NOx sensors, and notify a user of the state of the SCR inlet and outlet NOx sensors, the state including at least one of an operational state and that at least one of the SCR inlet and outlet NOx sensors are faulty.