Subaru uses several variations on their all wheel drive system, each of which features improvements over previous versions. As the years have passed, the vehicles have become more sophisticated, especially the WRX and WRX STi models. Subaru has been making AWD vehicles since 1972, and has learned a little something about it in the interim. Starting in 1996, every non-minicar Subaru features an all-wheel-drive system. The differences basically boil down into three areas: Differentials, the center differential, and computer control.
The "Standard H" is a pattern of positions into which the gear shift lever of a manual transmission may be pushed or pulled in order to change the gears used to drive the vehicle forward. This layout is used by the vast majority of transmissions and runs top to bottom, left to right
An automobile's differential gear (often abbreviated "diff", and most commonly referred to as the "differential") is a device which, potentially among other things, allows the wheels to be driven at different speeds. In a turn, the wheels (all of them, but we are currently interested in those which are driven, meaning that power is applied to the road or other surface through them) travel different distances in the same period of time, so this is important. Generally speaking, nearly every car needs a differential of some sort.
All Wheel Drive (AWD) is a system in which all wheels on a vehicle are driven, meaning that power is applied to the road (or other surface) through each of them. The benefits of AWD are all derived from increased traction, and include better acceleration and superior road holding, especially when roads are slick.
The following is a potentially incomplete list of the standard OBD-II powertrain codes. Manufacturers are free to add their own codes as they see fit, just as they are free to use unspecified pins on the connector.
The Ford Modular Engine (AKA "Mod V6", "Mod V8", et cetera) engine is the basis of practically every V8-powered vehicle made by Ford Motor Company (FoMoCo) in existence today. It is also the basis of the V10 powerplant inserted into a prototype Mustang and several Ford trucks. The "Modular" name has little to do with the motor, but on the manufacturing methodology; the plants can be retooled to put out different versions of the Modular powerplant in a matter of hours.7
A vehicle's engine provides motive power by consuming fuel, as opposed to an electric motor which uses electrical energy (current and potential) in order to produce rotation.