15801A - Customer Satisfaction Program. This bulletin is being revised to add a note at the beginning of the Service Information section. The 2016 model year GMC Sierra HD vehicle, and an increase in population has also been added. Vehicles equipped with Duramax Diesel Engine (RPO LGH or LML) and Ambulance Upfitter or Fire Truck Upfitter (RPO YF2 or ANM), may have a condition in which the emission control system as designed will limit speed under certain conditions. The EPA has approved General Motor?s request to remove the emission control system speed limitations on these emergency vehicles where applicable. Dealers are to reprogram the Engine Control Module (ECM) with new calibration for emergency vehicles, which will remove the emission control system speed limitations, and also provide an earlier warning for Diesel Particulate Filter (DPF) regeneration.