components for the vehicle which enhance the operation or extend longevity; for example: greasing systems, radio, air conditioning and extra lights. Although some accessories are non-essential to the vehicle operation, they are sometimes required in extreme operating environments.
auxiliary braking systems
secondary braking systems which slow or hold the vehicle by unconventional means such as:
- retarding the engine with compression brakes or exhaust brakes;
- utilizing a fluid coupler; or
- creating resistance on the driveline.
base engine
assembled block and head including internal components and gear trains.
diagnose
tasks involved in inspecting, testing and determining faults in vehicle systems and components.
drive train
mechanical portion that transfers power from the flywheel to the tires.
driveline (drive shaft)
drive connection between a power source and a driven component.
electronic control module (ECM)
module which controls functions of a vehicle; some common ECMs are EPUs (electronic processing units), ECUs (electronic control units), VECUs (vehicle electronic control units)
electrical systems
starting, charging, lighting and accessory circuits without computer control modules.
electronic systems
electrical systems operated via computerized electronic control modules and related sensors and wiring.
hydrodynamic system
hydraulic system with low pressure and high volume; torque converters and fluid couplers are based on this system.
hydrostatic system
hydraulic system which uses high pressure and low volume to transmit power through tubes or hoses to auxiliary systems.
landing gear
components which are used to support the weight of the trailer when disconnected from the vehicle.
power take-off (PTO)
device that couples and uncouples a power source to transfer power to auxiliary systems.
sensory inspection
diagnosing or inspecting using sight, sound, smell and feel.
repair
activities which include replacement, rebuild, or repairing of truck and transport vehicles and components
service
activities which include adjustment, lubricating and general maintenance of truck and transport vehicles and components.
spark ignition system
system which controls a small amount of electrical power to create and transmit, through a step-up transformer, a high voltage to a sparking device which in turn begins ignition.
suspension
components which absorb road surface irregularities to smooth vehicle ride; it is designed to permit controlled wheel movement over irregular surfaces; basic types include spring, air and rubber block
