As I understand it all GM cars before 94 were OBD-I.

Unfortunately borrowing one is not an option because with cars this old it's
the kind of tool that would get used alot, and since it is just a serial
stream I can't justify the expense in buying one (it's just a hyperterminal
with a few lookup tables after all!!). :) TTYL

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Pic Dude
> Sent: Tuesday, February 26, 2002 12:39
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]: OBDI tools?
>
>
> First, verify that it's OBD-I and not OBD-II.  You should be able to do
> a web search for the OBD-I protocol spec, but not sure if that would be
> published for OBD-II.  Output should be codes (not sure of format) with
> a "standard" format -- ie:  for OBD-II, the first char is the problem area
> (P=Powertrain, C=Chassis, B=Body, U=Network), the 1st digit is the
> mfgr or SAE, etc.  The next digit is a more specific area --
> ignition, fuel
> metering, emissions, etc, and the last couple are the actual trouble code.
> The tool may have a lookup table with the text messages, or you could
> look them up manually.  I'm sure OBD-I is different though, but you get
> the idea.  The actual protocol I'm unaware of.
>
> If you are doing this to develop a commercial product or really want
> to use a PIC, then may the force be with you.  Otherwise it may be
> better to borrow one, pick it up used, or run by a local Autozone,
> PepBoys, etc and use theirs for a few bucks.  Recently had a problem
> with my Audi, and it uses a VagCom -- an OBD-II with some Audi
> extensions.  Very expensive device, but I found a web site that lists
> VagCom owners around the US that will let you borrow for free or
> a beer, etc.
>
> Hope it helps,
> -Neil.
>
>
>
> ----- Original Message -----
> From: "Herbert Graf" <hgraf@EMAIL.COM>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Tuesday, February 26, 2002 10:18 AM
> Subject: [EE]: OBDI tools?
>
>
> > Have an '87 Buick Park Avenue we'd like to diagnos a problem
> on. It would
> > really be helpful if we had a "scan tool", however they are stupidly
> > expensive. I've done some searches and it looks like the data that comes
> out
> > of the ECM is simplly serial data at 8192bps at 12V voltage levels. Does
> > anybody have more info on this? Is the output text or is it just a bunch
> of
> > hex digits? If so anybody have a mapping for which hex digits mean what?
> For
> > now I'll be using a PC laptop but it sounds like this might be
> something I
> > can build with a PIC if I can find this info. Thanks for any help. TTYL
> >
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