Tom H,

great write up, it doses clear some of the unknows so far.

About the traction control on 94-95.

There is 2 differnet type of usage incorporated in the code. Analog and digital.
The analog is used on the y-bodies only. They have some crap bosch abs module.

The pcm sends pwm encoded signal of tps to ABS via pin A12[needs confirming]
Abs request spark retard from pcm via a frequency signal at pin A23??[needs confirming].

There is also second analog system to request traction on.
Put B+ to pin c12. It is analog on/off switch. Not sure where it is used. ??B-bodies.

The digital system is used on f-bodies.

The abs sends some message to pcm via ALDL bus, Requesting spark control and retard on/off.
The pcm sends scheduled messages to abs with some engine parameters.


On the ALDL bus there are some messages scheduled for dumping.
F0 is broadcast message with bus master id.
Others are some passive data send to other modules. It is very unlikely there is a 2 way communcation between modules.
Mode 7 is used if a module request data from pcm.
AS used in y-body ccm to pcm. There the ccm is the bus master and request data from pcm, then interprets the data and send it to other modules.
The 40 41 is extra theft system used on y-bodies only.