P4 ALDL information request

[Ken Kelly]

Kevin,
	Have you looked at Dave Hempsteads Web Page?

http://www.geocities.com/MotorCity/Shop/1624/95cam2.html

He has a scanner running for 94-95 LT1 engines, and has some
information about scan codes their.

		Ken

Kevin Day wrote:
> 
> Greetings!
> 
> I am new here, and new to ECM hacking.  Ever since I got my first fuel
> injected car, I've wanted to hack the computer.  I was very pleased to
> discover that I'm not the only one to have this perverse idea.  My first
> project is to write some scantool type software, and perhaps build a
> sexy digital dashboard for my 93 LeSabre.  This is partly just to get my
> feet wet; I would like to eventually start hacking the ECM itself
> (because it's there, I guess :)
> 
> I am waiting for the service manual to arrive in the mail, so for the
> time being I am not sure exactly which PCM is in my (recently purchased)
> car.  It is a 8192 baud type, and I have managed to read the "chatter"
> from the PCM.  I haven't yet tried to send any commands.  What I would
> like to do is decipher these messages.  The "Turbo P4" document was
> helpful conceptually, but the format does not seem to jibe exactly with
> what I read.  This is what I'm getting, over and over, with the ignition
> on and engine off:
> 
> F0  56
> F4  C6
>         4A  58  42  00  00  1C
>         4A  58  42  00  00  1C
>         45  5C  42  80  00  35  76  00  8F  63
>         4A  58  42  00  00  1C
>         4A  58  42  00  00  1C
> F0  56  ...
> 
> I understand that the F0 56 is the "ping" message for a scantool.  The
> second message, though, is perplexing.  The C6 message length seems to
> be wrong - there are 34 data words, plus 56, so I would expect 8A
> instead.  Anybody know what is going on here, and what the 4A 58...
> message means?
> 
> Can someone point me to more information on this ALDL format?  I am
> hoping that it has been deciphered already... or, alternately, if the
> this PCM program has been disassembled (and maybe commented?) that would
> be amazingly cool.
> 
> Thanks...
> 
> Kevin