Engine codes for '84 T/A

[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. Here's what I mean:
OFFICIAL: for the 12 pin ALDL port.
Pin   Function                          My Connector has these pins
A       Ground                                  Pin     A
B       ALDL Diagnostics                                B
C                                                       C
D                                                       D
E       160 Baud data line
F                                                       F
G
H       8192 Baud data line
J
K
L
M

        The connector pinout is arranged in this fashion:
                F E D C B A
                G H J K L M

        The communications protocol seems to be to pull the diagnostics line 
high, and send the hex command "F4" down the data line. (Your choice of baud
rate.) You then release the diagnostics line and wait for your data. I base
this information on old documents I found at work involving automotive data
acquisition.

        Any help would be appreciated.

--- Dan.