4L80E / ALDL

[Niinikoski Juha]

Hi
I am new on the list and don't know if this is right place to start 4L80E
TCM thread ?

I have 97 N/A diesel Hummer with 4L80E electronic transmission. Some time
ago I decided to try to build a display unit with what you can watch few
most critical transmission parameters like temperature TCC slippage and
possible clutch slippage. So far I have managed to hack ALDL interface and
protocol. Of course this happened by the hard way. First I taught that
Hummer 97 Implementation where OBD-II because of OBD-II like connector but
it is ALDL 8192.

I have build couple of display prototypes. One with Motorola HC12 CPU and
4x40 LCD display.HC12 contains also 8-channell A/D converter. I have plan to
include some other measurements too.  Second one is really cheap build with
Microchip PIC16F84 "washing machine" processor and 2x20 LCD. If anybody is
interested I can provide more information about my projects.


Where I need help.
1.
 I am now stuck with decoding parameters what TCM provides. I have found
most easy / evident ones like RPMs, temperature, selector switches etc. Most
of the response data is still unknown for me. Do anyone have documents or
more information about 4L80E ALDL commands / responses ?

2.
What is the right way to start communication with TCM. I have figured out
that read parameters command is F5 57 01 00 B3 but you need to give command
twice first time. After ALDL bus have "woken up" you need only one command
to get response. If you do not issue new commands within about one second
bus goes to sleep mode again. Are there some sort of wake up procedure or is
this (sending first command two times) right way to do it ?

Juha Niinikoski
Espoo Finland
97 N/A Diesel Hummer