On-board diagnostics (OBD) is a term referring to a vehicle's self-diagnostic and reporting capability. OBD systems give the vehicle owner or repair technician access to the status of the various vehicle sub-systems. The amount of diagnostic information available via OBD has varied widely since its introduction in the early 1980s versions of on-board vehicle computers. Early versions of OBD would simply illuminate a malfunction indicator light (MIL) or "idiot light" if a problem was detected, but would not provide any information as to the nature of the problem. Modern OBD implementations use a standardized digital communications port to provide real-time data in addition to a standardized series of diagnostic trouble codes, or DTCs, which allow a person to rapidly identify and remedy malfunctions within the vehicle. History 1968: Volkswagen introduces the first on-board computer system, in their fuel-injected Type 3 models. This system is entirely analog with no diagnostic capabilities. 1975: Bosch and Bendix EFI systems are adopted by major automotive manufacturers in an effort to improve tail pipe emissions. These systems are also analog in nature, though some provide rudimentary diagnostic capability through factory tools, such as the Kent Moore J-25400, compatible with the Datsun 280Z, and the Cadillac Seville. 1980: General Motors introduces the first data link on their 1980 Eldorado and Seville models. Diagnostic Trouble Codes (DTC's) are displayed through the electronic climate control system's digital readout when in diagnostic mode. 1981: General Motors introduces its "Computer Command Control" system on all US passenger vehicles for model year 1981. Included in this system is a proprietary 5-pin ALDL interfaces with the Engine Control Module (ECM) to initiate a diagnostic request and provide a serial data stream. The protocol communicates at 160 baud with Pulse-width modulation (PWM) signaling and monitors all engine management functions. Real-time sensor data, component overrides, and Diagnostic Trouble Codes. The specification for this link is as defined by GM's Emissions Control System Project Center document XDE-5024B. 1982: RCA defines an analog STE/ICE vehicle diagnostic standard used in the CUCV, M60 tank and other military vehicles of the era for the US Army. 1986: General Motors introduces an upgraded version of the ALDL protocol, which communicates at 8192 baud with half-duplex UART signaling on some models. 1988: The California Air Resources Board (CARB) requires that all new vehicles sold in California in 1988 and newer vehicles have some basic OBD capability. These requirements are generally