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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883


Understanding autospeak

Understanding the definitions of automotive terminology can help you understand your vehicle better.  It will also help with auto service department communication.  For starters, here’s some autospeak for each letter of the alphabet.

A-pillar:  The structural support on either side of the windshield, just ahead of the doors.

B-pillar:  The structural support just behind the front door.  Pillarless hardtops don’t have this support.

C-pillar:  The structural support just behind the rear door, supporting the rear of the roof.

Diagnostic code:  A two-digit “trouble” code that technicians retrieve with a scanner to aid in diagnosis, usually triggering the check engine light.

ECM:  An acronym for Electronic Control Module, an on-board computer that controls engine management, diagnostics, fuel delivery, and emissions.

Fifth wheel:  A coupler mounted on the back of a truck used to connect a semi-trailer — also used in the back of heavy-duty pickups to connect travel trailers.   

GVWR:  An acronym for Gross Vehicle Weight Rating, referring to the maximum vehicle weight capacity including passengers, cargo, and fuel.

Hydroplane:  The phenomenon of a tire lifted by a layer of water on the road surface rather than making contact with the pavement.  Due to insufficient tread, too much water, or both, the water can’t be displaced fast enough from under the tire.

Injector:  A nozzle used to deliver fuel to the engine in an atomized spray pattern  — same as fuel injector.

Jet:  A small orifice in a carburetor used to meter fuel flow.

Knock Sensor:  An engine sensor that tells the ECM when spark knock is detected, momentarily retarding ignition timing until detonation ceases.

Lexan:  The trademark name for a clear shatterproof clear plastic used for many modern headlamp coverings.

Macpherson Strut:  A type of front suspension where the shock absorber is mounted beneath the coil spring.

Nitrous Oxide:  An explosive gas (N2O) mixed with gasoline to increase the efficiency of combustion and raise horsepower.

Oxygen Sensor:  A sensor in the exhaust used to measure completeness of combustion, signaling the ECM to adjust fuel delivery accordingly.

PCV Valve:  PCV is an acronym for Positive Crankcase Ventilation.  The device is a one-way valve that allows for the recycling of crankcase fumes.

Quarter Panel:  A welded-in panel usually at the rear sides of a vehicle.  Often referred to as a fender — that’s wrong since fenders are bolted on.  A front “fender” is actually a quarter panel if welded on, for example on a Karmen-Ghia.

R-134A:  A CFC-free air conditioning refrigerant used in most modern vehicles.

Supercharger:  A compressor (usually belt driven) used to force-feed air to an engine.

Turbocharger:  An exhaust gas driven “supercharger” with turbine-like design.

Undercarriage:  The chassis of a vehicle.

Viscosity:  The resistance of a fluid to flowing.

Wheel Base:  The distance from the center of the front wheels to the center of the back wheels of a vehicle.

Xenon:  An element that is a gas at room temperature — used in making bright white automotive lamps.

Y-pipe:  A Y-shaped exhaust pipe that merges two passages into one — many Subaru owners have learned about these.

Zerk fitting:  A nipple-like lubrication fitting through which grease is applied to a chassis or suspension joint.

There you have it — throw those terms around and it might seem as though you know what you are talking about.

Readers may contact Bill Love via e-mail at