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Hey Mike, hope this helps.

ECM
An "ECM" is an Engine Control Module, sometimes referred to as an "ECU," or Engine Control Unit. This computer takes incoming sensor data to alter the function of electronic systems. The first ECMs introduced in the early 1980s could only control fuel injection, but as electronics and engine design have improved, the function of these devices has spread to almost every aspect of operation. In a modern engine, the ECM will gather information from the intake, exhaust, cooling system and several internal components to judge the running condition of the engine. From there, it can decide the position of the camshafts, the throttle position, ignition timing, fuel injection timing and, in turbocharged cars, wastegate pressure.

TCM
Some cars also have a "TCM," or Transmission Control Module. This device uses incoming sensor data to determine when the transmission needs to shift. Over the years, the functionality of these devices have improved, adding input from the cruise control, throttle and traction control system, reducing gear hunting and wheel spin. Electronically-controlled automatics have TCMs as do dual clutch manual transmissions, but traditional manual transmissions do not. Electronic functions for manual transmissions are done by the ECU if at all. For example, Corvette's Active Rev Matching matches clutch and engine RPM during shifts using wheel speed data from the traction control system and a shifter position sensor on the transmission.
 

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The Legend has only the ECU that manage engine and transmission. So in the cars with manual transmission or Automatik transmission are different ECU's.

Greetings
Ralph
 
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