- U -

U

Uranium An element with the atomic number of 92.

U-Bolt

U-shaped bolts to fit around the rear-axle housing for clamping the leaf spring to the housing.

U-Joint

A short term for universal joint.

U-tube

A term used for manomometer.

U.S.

An acronym for United States.

U/

Under.

UART

Universal Asynchronous Receive and Transmit. A type of data stream used on non-OBD-II diagnostic systems. UART toggles between 5 volts (positive) and 0 volts.

UDOT

Utah Department of Transportation.

UIM

Universal ignition module.

Ultrahigh Frequency (UHF)

The band of signal frequencies falling between 300 and 3000 MHz.

Ultraviolet

An invisible spectrum with wavelengths shorter than visible light b longer than X-rays about 200 to 4000 angstrom units.

Ultraviolet Light

A light source used in non-destructive testing for cracks in metal parts.

Umbrella Seal

An umbrella-shaped valve stem seal used to direct oil away from the stem and guide.

Unburned Hydrocarbons

HC is a major pollutant in exhaust gases as a result of the partially unburned fuel after combustion.

UNC

An acronym for Unified National Coarse. Identifying a standard thread pitch and count.

Under-Dash Unit

A term used for hang on unit such as for a CB radio or other aftermarket accessory.

Under-Hood Lubrication Services

The work performed under the hood during a chassis lubrication such as lubricating the distributor, manifold heat-Control valve, upper suspension, hood hinges and latch, checking the fluid in the engine crankcase, brake master cylinder, radiator, battery, and power steering reservoir, plus inspecting belts and safety-related items.

Under-Vehicle Lubrication Services

Work performed under the vehicle during a chassis lubrication such as changing oil and filter, checking or changing transmission fluid, and gear oil or differential gear oil, lubricating the suspension and steering system, universal joints, clutch ans/or transmission linkage, front-wheel bearings, and inspection of safety-related items.

Undercarriage

The chassis of a vehicle.

Undercharge

An air-conditioning system that is short of refrigerant, resulting in improper cooling.