Direct ignition: An ignition systems without any distributor, wherein the spark distribution is controlled by the computer.

Diode: It is a basic electronic component formed by combining a N-type and a P-type semi-conductor back-to-back. Diodes are commonly used as rectifiers.

Digital fuel injection (DFI): A system, identical to earlier electronic fuel injection system, but with digital microprocessors. In this analog inputs from various engine sensors…

Diesel Particulate Matter (DPM): Sub-micron size particles found in the exhaust of a diesel engine. DPM consists of both solid and liquid particles and is…

Diesel Particulate Filter (DPF): A filter which removes small particles from exhaust of a diesel engine.

Dieseling: A condition in which an S.I. engine continues to run for some time after the ignition is turned off; caused by the hot spots…

Diesel index: Diesel index is defined as: Diesel index = Aniline point (°F) x API gravity (deg)/100

Diagnostic socket: A socket on the vehicle, usually located in the engine compartment, which is part of the onboard electronic sensor system.

Diagnostics: Process of identifying the cause or nature of a condition or problem to determine the appropriate corrective action to take for repairing an automotive…

Diagnostic code: Code number obtained by accessing the diagnostic mode of the engine management computer. This code can be used to determine the area in…

Detonation sensor: A sensor, which is often piezoelectric, mounted near the cylinders which can detect engine knocking or frequencies of detonation so as to send…

Detonation: An uncontrolled explosion of the unburnt air-fuel mixture in the engine cylinder occurring after the regular combustion of some of the charge caused by…

De NOx catalyst: A catalyst which, unlike a conventional catalyst used in a three-way catalytic converter is able to remove NOx from the exhaust gases…

Deep cycling: The process of discharging a battery almost completely before recharging.

Dead centre: The extreme top or bottom of the piston stroke.