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DM

A Mercedes acronym for Diagnostic Module-Emission Monitor.

DMCV

Deceleration mixture control valve.

DME

Digital motor electronics.

DMIVA

Distributor mounted ignition module with vacuum advance.

DMM

Digital multi-meter.

DMS

Dual manifold system.

DMV

Department of Motor Vehicles or distributor modulator valve.

DNF

An acronym for "did not finish".

Do-it-yourself (DIY)

To repair one's vehicle.

Do-it-yourselfer (DIYer)

One known to repair their own vehicles.

Dobson Unit (DU)

A measure of ozone density level, named after Gordon Dobson, a British meteorologist, who was the indenter of the measuring device (called a spectrophotometer).

DOE

Department of Energy.

Dog

1. A poor performing vehicle. 2. To follow another car very closely in oval-track racing. 3. A pin or stub used to mate and/or drive a gear or assembly.

Dog Box

A tool box-style metal carrier that is designed to transport hunting dogs either in the bed of a pickup truck or in the cargo area of an SUV or van. Dog boxes typically are insulated and feature special ventilation to keep the dogs safe and comfortable. Some dog boxes also include a lockable storage compartment on top to secure guns, ammunition and other supplies. Dog boxes usually are made by companies that manufacture tool boxes, and typically are offered in aluminum diamond plate or steel.

Dog Clutch

1. A simple splined clutch that cannot be slipped; generally found in dirt-track cars without transmissions. 2. The mating collars, flanges, or lugs that can be moved as desired to engage or disengage similar collars, flanges, or lugs in order to transmit rotary motion.

Dog House

1. The housing over an engine or transmission. 2. The front fenders, grille, and hod assembly of a vehicle.

Dog Leg

A sharp, angular turn.

Dog Tie-down System

A leash-type device that is designed to secure a dog in the bed of a pickup truck, both so he can't jump out and so he won't go flying or get hurt in the event of an accident. Some sort of dog restraint is required by law in many states.

Dog Tracking

Off-center tracking of rear wheels as related to the front wheels.

DOHC

An acronym for dual overhead camshaft.