Automotive diesel technicians and mechanics are responsible for the maintenance and repair of diesel-powered vehicles. Their duties include running diagnostic tests on vehicles, test driving vehicles to gauge performance and maintaining detailed records of the vehicles they have serviced. Diesel engine maintenance and repair is becoming more complex as engines and other components use more electronic systems to control their operation. For example, fuel injection and engine timing systems rely on microprocessors to maximize fuel efficiency and minimize harmful emissions. In most shops, workers often use hand-held or laptop computers to diagnose problems and adjust engine functions. Technicians and mechanics must be equip to use a variety of complex power and machine tools like pneumatic wrenches, lathes, grinding machines, and welding equipment. Hand tools, including pliers, sockets and ratchets, and screwdrivers, are also commonly used.