P4 ALDL information request

[Kevin Day]

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