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 NO sensor upstream of the close-coupled selective catalytic reduction system, a second NO sensor between the two selective catalytic reduction systems, and a third NO sensor downstream of the underbody selective catalytic reduction system. The engine control unit may perform methods allowing intrusive diagnostics to be performed on exhaust gas NO sensors using the selective catalytic reduction systems during normal operation of the heavy-duty truck.