OBD is a abreviation for On Board Diagnostics.
OBD-1 is in reference to Title 13 California Code 1968 tiltled "Malfunction and Diagnostic System for 1988 and Subsequent Model Year Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles with Three-Way Catalyst Systems and Feedback Control." filed on 11-15-85.
This required cars sold in California to have a on-board computer processor for on-board self diagnostics of computer sensed emission related components, fuel metering device and EGR (exhaust gas recirculation system). A partial or total malfunction that exceeded exhaust emission standard would illuminate a MIL (malfunction indicator light) and provide on-board indentification of the malfunction location. To provide malfunction location information, codes are stored in on-board computer memory. To read codes manufactures use methods, such as flashing MIL light or various serial data protocols.
OBD-2 is in reference to Title 13 California Code 1968.1
titled "Malfunction and Diagnostic System Requirements-1994
and Subsequent Model-Year Passenger Cars, Light-Duty Trucks,
and Medium-Duty Vehicles and Engines. filed on 8-27-90 to Air Resouce Board (ARB)
This requires a standard electrical connector, open source standarized diagnostic trouble codes (DTC), data, and communication protocol with more specific self-diagnostic on-board monitoring of emission malfunctions.
The 12 step system monitoring requirements or