4L80E TCM ALDL data display

Page updated 17.09.2003

This is another old project.



There is electrically controlled 4L80E transmission in my 6,5l NA Diesel Hummer. From day one I was interested to be able to read data from my 4L80E-transmission controller (TCM) . I of course tried to find information about TCM boxes and their data streams. I found practically no information about this particular subject. So I had to start from scratch.

First misleading thing was OBD-II like connector what Hummer is using with its 8192bd ALDL TCM. After I discovered this I started to think how to get any communications with TCM. Taking TCM out from car and disassembling it was not very attractive option. In Hummer TCM is located in difficult place and I did not have spare unit. Things started to rock when I managed to borrow Snap On scanner. With scanner I discovered how to start communication with TCM. Next step was to build simple TCM data stream emulator. With this emulator connected to scanner I discovered most of interesting data stream parameters and their scaling. After this I did display unit and wrote small program for TCM communication and parameter scaling.

Current situation (after four years)

I have not done much since initial try. I still do not have any official definition for data stream. I have learned more about general 8192 ALDL command and response structures and know that my initial interpretation is not right. Display program however works and I have been too lazy to correct just this.



TCM box in this application is: Service number 16196390 with BRZY calibration



I used small Axman made Motorola HC12A4 evaluation board for this project. This board is connected to Varitronix 4*40 LCD display. Level shifters and some other small circuits are done on prototype board.



I am sorry no schematics have ever been drawn. You have to find out from the source code how to connect LCD and other signals.



Source code

S19 file



Some extras

I installed two pressure transducers and few temperature transmitters to monitor




Ugly box

Display page #1

Display page #2

Display page#3

Display page #4



Other information


Link to old project page