OBD : "ON BOARD DIAGNOSTICS"    REDUX-1 More simple          

 In the USA, OBD has a special meaning, it was mandated here (EPA FED 1990/Calif. ARB  in 1988) and became the law, but in practice , before the LAWs  here, the technology existed  (USA is here) in our major car makers (see GM below).
Califonia led the way,1988  the proof is this document from the SAE.org. ($25 to read it, and not what that...)

"On board " means , inside the ECU/PCM the Allen Turning BRAIN, that  runs Back-Ground jobs (tests) at all times checking for errors or discovers an engine that is  no longer smog clean! (ask VW how they do that? LOL ?)

"The 1990 Act also established the requirement that passenger vehicles be equipped with on board diagnostics as recommended by SAE.ORG
SAE actually petitioned the USA governments to use, OBD technology, before 1988. The USA law makers agreed , end story until OBD2.

I think the GM ECU first with trouble codes is 1982 (or late 81)  as of now you have and error light CEL and can scan the ECU for errors. (OBD is kinda born here, but was custom to GM) GM had this back in 1982 (ALDL)

ISO and SAE published standards (USA  only)

End short history. (next is Suzuki OBD1 only)

OBD1,  1989 to 1995 at Suzuki , market codes  03 USA FED and 33 USA CALIF.   FACT IS Suzuki never publised the protocols, only the map seen in the (eg 1995 FSM)
The OBD1 Suzuki cars do have home made , hacker made scan tools, Seen here. (low cost too....)
Fact 1, there is no world OBD1 communications standard! nor do 2 car makers use the same OBD1 commuication protocols.  (but most cars you can match up a scan tool to each car, but is expensive, to do with so many cars.)
Fact 2, the USA invented OBD2,  and only our tools work for OUR standard , but sure other countries have copied ours or cloned it, or upgraded it to their needs.  Like EU, EOBD or JAPANS JOBD.  (so I have 1 tool and fits all cars here in USA, 1 tool)
Fact 3: most countries failed to do any of that until 2001 or 2006 or later.... a hard cold fact.  read this again.
What countries support OBD1 or 2? "
Fact 3: Each car company (and country) has there own OBD scan too protocal, levels, pins, connectors and command structures,  (many have never been published)
Fact 4: All USA cars (1998+ Canada) 1996 and newer can be scanned with any store bought new scan tool, our Suzuki 1996-1998 any tool sold here works. ALL!


Here is my OBD facts page,  deeper we go...

ver 7-------------- 7-16-2011  7-26-2015 redux  (covering only USA cars,  and our tools)