Spartan Motors USA (Spartan) is recalling certain 2001-2018 Spartan Gladiator, Diamond, MetroStar, and Advantage emergency response vehicles. The affected vehicles may not be equipped with a pressure protection valve installed between the air reservoir and the lubrication control module. If the air line were to become disconnected between the lubrication control module and the air reservoir, a loss of air to the air brake system could occur. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard (FMVSS) number 121, “Air Brake Systems.”