E67 and TCM controler question

[EVI]

I am tuning a H3 with a LS7 engine. The pcm is a E67 with a separate stock TCM using a 4L70E. I'm not very educated on the can bus stuff. Could some explain how it works or at least tell me if I can tune the TCM like it was a stand alone. Do I have to tune the PCM and TCM a certain way so they can talk to each other.

[ScarabEpic22]

You have to tune both seperately, as in you have to select E67 ECM one time to read the ECM out, save it, then go back and read the T42 TCM and save it. They are completely independent of each other for tuning purposes (well they do communicate during operation but for tuning they are seperate) as in you have to edit the ECM and then edit the TCM and perform 2 flashes. Just dont set the values to crazy ones and you wont have any problems! Its ok, Im coming from a P10 PCM (4.2L I6 only) to my TrailBlazer SS with an E67/T42 combo (6.0L LS2/4L70E combo) so its different for me too!

[EVI]

Thank for the reply. I understand that they have to be flashed separately, but in the torque management tables, which computer senses how much torque the engine is delivering. What sensor is used to determine this? Is it calculated to the MAP or is there something in the trans? I don't know. If the computers are separate but talk to each other then why? Is it just to make sure everything is working properly? Maybe for fault codes or does one computer help decide what the other is going to do?

[ScarabEpic22]

I think they talk from more of a rationale purpose, for TM Im think they both figure how much TQ is delivered? For example there are a few tables related to TM and traction control (for my LS2 at least) in the ECM and in the TCM there are the TQ reduction based on gear tables. Im not really sure if the ECM calculates how much TQ the engine is making then passes this as a signal to the TCM but thats what would make sense as the TCM has TQ referenced tables.

Honestly I think the reason for 2 seperate controllers is so GM can use a fewer number of controllers with different OSs for lots of cars. Like the same ECM is used in my TrailBlazer SS, 08+ regular TBs, 08+ Colorado/Canyons/H3, and a LOT more. Same for the TCM, all the 4L60/65/70Es are controlled by the T42 in lots of different platforms.

Can someone else enlighten us on how the ECM/TCM communicate desired and delivered TQ values?

[GMPX]

The torque values are all calculated (sorry, don't know the 'exact' method).
So the ECM sends out calculated torque values to the TCM (and anything else on the CAN bus), the TCM can also request torque reduction to the ECM as well.

Erik is correct on the logic behind the separate ECM / TCM. It allows for a universal controller that can 'easily' be adapted to any appication.
You just have to look at how many cars / trucks use the T42 TCM to realise it was a wise move.

Cheers,
Ross