Engine codes for '84 T/A

[Donald Whisnant]

>
>From: FIScot at aol.com
>Date: Sun, 21 Jan 1996 20:40:54 -0500
>Subject: Re: Engine codes for '84 T/A
>
>    Subj:   Engine codes for '84 T/A
>    Date:   96-01-21 13:31:47 EST
>    From:   ws6transam at voyager.net (Daniel R Burk)
>
>  > Does anyone have the hexadecimal engine codes for the GM ALDL computers
>  > as used in '82 through '92?  I have an '84 that I want to begin
>  > communicating with, but I do not know which addresses I need to poll to
>  > receive the engine diagnostics data.  So far I have struck out in
>  > finding them via the random method.  Also, the ALDL interface seems to
>  > have the pins in the wrong locations than the "official" designation.

>  <snip>

Scott and Dan:

I have several of the older ECM's that I want to communicate with also (we've
talked about this a little before Dan).  I am putting a new engine (a '93
4.3L Vortec V6) into my '85 Grand Prix.  The new engine came complete with
its own ECM.  What I want to do is first communicate to the old ECM.  And then
to the new '93 ECM.  Question 1) Where did you guys obtain this data on the
ALDL port of the 8192 baud rate spec and 160 baud ALDL diag box??  I have the
SAE HS-3000 doc, but it basically only talks about the newer OBD-II, which
will come in handy later when I start tinkering on my '95 Firebird...  Question
2) I have been trying to read the old ROM in the '85 ECM without success.  I've
been told that it is just a mask programmed version of the 2732.  But one of
my eprom programmers just reads all 0's and the other just reads all 1's --
the conclusion I drew was that the chip isn't getting enabled and the 0 and 1
difference is the difference in the pull-ups used on the two units.  Has anyone
else tried this and/or has a solution?? -- I've contemplated using several
cpu output ports and just writing ALL possible binary combinations to ALL lines
on the chip via current limiting resistors and then use a set of input ports
to read the pins at the chip side of the resistors.  This will do 2 things:
it will tell me an exact pin out -- after I sort through the data -- and it
will tell me how to enable the stupid thing...    Any idea guys???

I've got a meeting Thursday with an engineer and a rep from Harris on their
OBD-II J1850 communcations chips and I've got a conference scheduled with
Motorola with one of their engineers and reps on the same.  Eventually, I
will be able to communicate with this blasted ECMs and PCMs...

Donald Whisnant
dewhisna at ix.netcom.com