Control reset and diagnostic to maintain tailpipe compliance

A selective catalytic reduction reductant injection control module including a processor and a non-volatile memory including a set of instructions which are configured to cause the processor to:

• determine an amount of nitrogen oxide compounds (NOx) present in a tailpipe at a first location upstream of a reductant injector to define a determined upstream NOx amount;
• determine an amount of NOx present in the tailpipe at a second location downstream of the reductant injector to define a determined downstream NOx amount;
• subtract the determined upstream NOx amount from the determined downstream NOx amount to define a subtracted NOx value;
• determine a cumulative difference based on the subtracted NOx value;
• determine whether the cumulative difference exceeds a control threshold;
• set a selected upstream NOx value as a predetermined model upstream NOx amount if the cumulative difference exceeds the control threshold;
• and
• set the selected upstream NOx value as the determined upstream NOx amount if the cumulative difference does not exceed the control threshold.

A vehicle system comprising:

• a tailpipe assembly defining an exhaust conduit;
• a selective catalytic reduction system including a reductant injector, the reductant injector configured to inject a reductant into fluid communication with the exhaust conduit of the tailpipe assembly;
• an upstream NOx sensor configured to measure nitrogen oxide compounds (NOx) in an exhaust flow stream within the exhaust conduit, the upstream NOx sensor being disposed in fluid communication with the exhaust conduit at a first location upstream of the selective catalytic reduction system;
• a downstream NOx sensor configured to measure NOx in the exhaust flow stream within the exhaust conduit, the downstream NOx sensor being disposed in fluid communication with the exhaust conduit at a second location downstream of the reductant injector;
• and
• a reductant injection control module including a processor and a non-volatile memory including a set of instructions configured to cause the processor to:
• determine an amount of NOx present in the exhaust conduit based on an upstream signal from the upstream NOx sensor to define a determined upstream NOx amount;
• determine an amount of NOx present in the exhaust conduit based on a downstream signal from the downstream NOx sensor to define a determined downstream NOx amount;
• subtract the determined upstream NOx amount from the determined downstream NOx amount to define a subtracted NOx value;
• determine a cumulative difference based on the subtracted NOx value;
• determine whether the cumulative difference exceeds a control threshold;
• set a selected upstream NOx value as a predetermined model upstream NOx amount if the cumulative difference exceeds the control threshold;
• and
• set the selected upstream NOx value as the determined upstream NOx amount if the cumulative difference does not exceed the control threshold.