Originally Posted by bartonmd
So you guys will have to help me out... All of my schooling on automotive electronic control was based on what was mostly out in 2001-2002 (when I was doing my specialization), so a "PCM"... On the seperately controlled ECM/TCM, what's the deal? It sounds like the TCM says "you're making too much power for this gear/range, stop that" and tells the ECM to pull timing (or I assume, partially close the throttle), even when there is no shifting happening (or rather, not because of a shift)?
It is my understanding GM went from a combined PCM (engine + trans) to a seperate ECM and TCM in order to use them on more vehicles.
They communicate a lot with each other, you cant flash whatever TCM tune in and have it work, some do but most do weird things like take away the shift indicator and report you're going 255mph at a stop.
Yes, the TCM and ECM both have limits in them that can reduce power if they determine too much is being made. These tables are commonly maxed out when installing a built engine and/or super/turbocharger otherwise you'll be in 2nd gear at 80% throttle and the ECM will be closing the throttle and possibly pulling spark. It even can happen on stock cars sometimes, Ive had my 02 pull timing and close the throttle with the stock tune in it when I was beating on it.
Im not explaining this very well I know, hope you can understand my rambling.