I need a schematic, link, data, etc. Shouldn't the ECU be the "Boss" over all the control "Departments" and the TCU be the "Supervisor" over the transmission. The boss gets busted for fraud and inefficiency. Turns out the TCU was in on the job. Fire the boss, and the TCU goes down with it.
Let me put it to you this way. Take out the TCU and try to drive your car.
The ECU only supplies the vital information to the TCU.