NOX SENSOR DIAGNOSTICS IN HEAVY-DUTY MOTOR VEHICLE ENGINES

A heavy-duty truck has a diesel engine, an exhaust after-treatment system, and an engine control unit. The exhaust after-treatment system includes a close-coupled selective catalytic reduction system and an underbody selective catalytic reduction system, a first NOsensor upstream of the close-coupled selective catalytic reduction system, a second NOsensor between the two selective catalytic reduction systems, and a third NOsensor downstream of the underbody selective catalytic reduction system. The engine control unit may perform methods allowing intrusive diagnostics to be performed on exhaust gas NOsensors using the selective catalytic reduction systems during normal operation of the heavy-duty truck.