Diesel service technicians and mechanics, also known as bus and truck mechanics and diesel engine specialists , repair and maintain the diesel engines that power transportation equipment such as heavy trucks, buses, and locomotives. Some diesel technicians and mechanics also work on heavy vehicles and mobile equipment, including bulldozers, cranes, road graders, farm tractors, and combines. A small number of technicians repair diesel-powered passenger automobiles, light trucks, or boats. (For information on technicians and mechanics working primarily on automobiles, heavy vehicles, mobile equipment, or boats, see the Handbook statements on automotive, heavy vehicle, and mobile equipment; and small engine service mechanics).