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