Title: OBD hard facts ? REDUX-1  A 100% U.S.A. Perspective. Gasoline only, light cars and trucks < 8500 lbs                                    

Suzuki OBD1: Suzuki Data link SDL.  See it work here with free software and $60 cable.
End OBD1 malarkey....
OBD2 ONLY next:
This chapter 2 on topic  has nothing to do with Airbag scans , or ABS or TPMS. (only PCM scans (ECU). 
There are no USA spec rules (laws) for those pins, for ABS etc, nor protocols. (only fuel and smog controls are protocol /logic regulated, except in VWs slanted world)
EFI or electronic fuel injection systems are a complex topic, (with 5 Generations of system, engines, and makers and bam , information overload.)

Starting in 1997, 4 speed, transmission errors now show up on the scan tool and the smog man can fail the just for transmission errors... Not fun that.

OBD2,  our car, Suzuki , USA 96+ or Canada 1998+ "ONLY"!   My full OBD2 page is here with real examples !. This socket TYPE and location is regulated by our laws.
NO NON N.American coverage here. (ever)
Be sure pin 16 is hot, if not  the FUSE IS BLOWN !  First things first as they say.

The make specific is where they add ABS, TPMS, Airbag controls etc.  (each maker desides that, not our LAWS)

ERRATA: (good luck convincing your SMOG MAN) but you can print this out (on the linked page) to prove these facts.
The 96 Suzuki (and GEO) are listed and limited compliance to OBD2 spec.

Not only that?, but look here at the official OBD2 cars that are WACKO !    this list shows USA OBD2 cars that are not 100% compliant , ie: buggy , faulty designs.

 Serious compatibility  issues using USA OBD2 scan tools  on non USA cars.


If your car is not  USA OBD2 certified, stop, no need to go further.  (1996 USA or 1998 in Canada or newer)
  1.  the car  battery is too low ,10v to 16 volts is the legal range or things go stupid.  Please do ,charge the battery up to 12.6vdc rested. or buy a new one.
  2. The Scan tool is dead  or COMM. failure, the batteries in the tool are dead or the DLC Pin16 car OBD2 port has a blown fuse. 
  3. The car is new (Can-Bus) and your tool is old and does not support CAN-bus
  4. The scan tool is super old (yes, I have one from 1995) and only does 1 of 4 signaling pin levels, so fails to work on 3 out of 4 cars made.  (time to upgrade fella)
  5. The tool is still dead.  The tool is for USA cars,  is your car a real USA car? If not , then buy a tool, or your car and for your country. Do not use USA tools on cars out side of the USA. or it will fail.  (if the hood sticker shows OBD2 cert , it will work)
  6. It's still dead but I forgot to notice the Dead CEL lamp key on, this means the ECU is dead, lost power or is in BACKUP mode. (brain dead mode)
  7. I can not clear the CEL lamp , that is because (for sure) there are LIVE errors, you can not erase live errors only the history can be erased. You  must find the DTC errors and look them up in the FSM, to find how to complete the tests and find the bad cause or part, or loose wire, etc.
  8. The monitors are now , not ready status  after a reset, this is 100% normal, and you must drive say 50miles, at 50mph and coast for all monitors to clear, and not have a full tank of gas , 1/2 full is best, or the EVAP monitor will hang, by design.
  9. Why do I get the wrong reason definitions for a specific DTC, code,  say a P2xxx code, that is because that code (pretend JEEP ) is a JEEP only code (only P0xxx) codes are generic or as we say, Federal codes.  Look up codes for your car, and engine, at alldata.com or the real FSM.
  10. The DTC keeps coming back,  sure, that means it real. The ECU will not lie you,  it's a real test, that really does fail every time the  ECU does the tests,  tests take from 1/10th second to report or 30minutes (EVAP checks.)
  11. Some PID'S are dead on my scan tool, that is because this ECU/PCM does not have such a sensor or PID for it, for example, you engine runs off MAP sensor and the MAF PID is dead or missing, All normal. On some older ECU 1996 , it may show missing sensors as 0000 or 9999.
  12. My VIN and other ID data are missing,  that is because we didn't have that prior to 2004. 
  13. No MPG PID,  that is correct early ECU's don't have that feature. Like my  Jeep 08 and 10 have...  (PID'S are live data, either sensors or math outputs like MPG, or Load)
  14. Why can't my scan tool or ECU, tell me what part is bad.  Answer:  Is too dumb, it can only report, tests that fail, some fancy scan tools have web connected helper links, that might tell, what to do, in geek language., just like the FSM does. (but 10x more accurate is the FSM)
  15. Why does my ECU/PCM show 5 errors (DTC) and only one thing is bad.  That is because that  if one little part fails it then fails  5 tests.   This is where humans beat computers 10 to 1, we can tell which  is the primary path.  (with practice, and gee that is skill you local mechanic has, use him/her)
  16. How can I solve all this, how to gain clarity, that is easy, gather more evidence, that is the job of the ASE tech., to take more tests, by hand to prove what is REALLY going on.  You must do that. or fail, or go broke guessing at parts.
  17. So you are telling me?, that  a $200 scan tool , does not replace humans? ,  and put out of work 700,000 automotive service technicians?   that know how to diagnosis problems and not simply guess, at your cost? BINGO.

Keep in mind, at all times, all sources of data, not out of the FSM , for your  car , are subject to errors, with vast errors on the internet.  
The FSM is OFFICIAL, there is no alternate to it , really, but alldata.com  comes the closest of all ,

rev 10 ++++ 11-06-2010  added examples.   2-27-2014 added pitfalls ,  added link to the best of the best.  REDUX, less is more, now... cleaned it all up. no redundancy.. easy peasy Japaneezy