749 question(s)

[alexpeper]

GM uses a SAE Class B network Carrier Sense Multiple Access (CSMA),  non-destructive contention resolution, bit arbitration,
priority frame, CRC. variable pulse width.  There is a set of standard legislated data common to all cars, but
O2 adjustment calibration is not included.
Alex
----- Original Message -----
From: Lou <lfaustini at atlantech.net>
To: <gmecm at diy-efi.org>
Sent: Sunday, October 01, 2000 7:24 PM
Subject: Re: 749 question(s)


>
>   Is there anywhere that I can get information on OBD-II communications?
> I would like to build an OBD-II to rs232 interface, and monitor my car's
> info. I have seen lots of products for sale that do this, but being an
> engineer geek, I want to understand exactly how OBD-II communications work.
> Is it RS-232 UART framing? Is it synchronous data like a T-1  Is there a set
> of
> (standard) commands, like "give me water temp" "adjust O2 calibration"
> and things like that. Basically, Where can I get info to learn this stuff? I
> hit
> the SAE web page, but they want to charge $$ for the standards, and
> having read ICD's before, I know how useless the can be sometimes,
> So, I put the question to you folks, the undisputed experts in reverse
> engineering automotive fuel systems.
>
>   Any help or links would be greatly appreciated.
>
>   Thanks !!!
>
>   ---Lou
>
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