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.
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
portion that transfers power from the power source to the tires.
driveline
part of the drive train that couples the power source to the driven component.
electrical systems
starting, charging, lighting and accessory circuits without computer control modules.
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), TCMs (transmission control modules), ABS (anti-lock braking systems).
electronic systems
electrical systems operated via computerized electronic control modules and related sensors and wiring.
high voltage
any voltage that is 50 V and above
landing gear
components which are used to support the weight of a semi-trailer when disconnected from the vehicle.
power take-off (PTO)
device that couples and uncouples a power source to transfer power to auxiliary systems.
repair
activities which include replacement, rebuild, or repairing of truck and transport vehicles and components.
sensory inspection
diagnosing or inspecting using sight, sound, smell and feel.
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.