Reductant tank sensor diagnostic method and system

A reductant tank sensor diagnostic system comprising:

• a reductant tank storing reductant;
• a doser;
• a tank level sensor;
• and
• a controller communicatively coupled to the tank level sensor and comprising:
• a recirculation circuit structured to cause recirculation of reductant from a reductant tank to a doser to cool the doser;
• a tank level sensing circuit structured to access a first value at a beginning of a monitored time period indicative of a first tank level value based on output from a tank level sensor;
• a reductant dosing circuit structured to access a plurality of reductant dosing command values over the monitored time period;
• a dosing integration circuit structured to determine a dosed reductant value for the monitored time period responsive to the plurality of reductant dosing command values reaching a threshold integrated value;
• the tank level sensing circuit further structured to access a second value at an end of a monitored time period indicative of a second tank level value based on output from a tank level sensor responsive to the dosed reductant value reaching the threshold integrated value;
• a dosing estimation circuit structured to determine a sensor-estimated dosing value for the monitored time period based on a difference between the first value and the second value;
• and
• a sensor diagnostic circuit structured to diagnose the sensor as performing outside of an acceptable calibration range based on a difference between the sensor-estimated dosing value and the dosed reductant value for the same monitored time period.

An apparatus for diagnosing a reductant tank sensor comprising:

• a recirculation circuit structured to cause recirculation of reductant from a reductant tank to a doser to cool the doser;
• a tank level sensing circuit structured to access a first value at a beginning of a monitored time period indicative of a first tank level value based on output from a tank level sensor;
• a reductant dosing circuit structured to access a plurality of reductant dosing command values over the monitored time period;
• a dosing integration circuit structured to determine a dosed reductant value for the monitored time period responsive to the plurality of reductant dosing command values reaching a threshold integrated value;
• the tank level sensing circuit further structured to access a second value at an end of a monitored time period indicative of a second tank level value based on output from a tank level sensor responsive to the dosed reductant value reaching the threshold integrated value;
• a dosing estimation circuit structured to determine a sensor-estimated dosing value for the monitored time period based on a difference between the first value and the second value;
• a sensor diagnostic circuit structured to diagnose the sensor as performing outside of an acceptable calibration range based on a difference between the sensor-estimated dosing value and the dosed reductant value for the same monitored time period;
• and
• a diagnostic transmission circuit structured to send a diagnostic decision to an on-board diagnostic system indicating that the sensor is performing outside of the acceptable calibration range.