ECU verus ECM, ECM verus PCM

ECU verus ECM, ECM verus PCM

What’s the difference between ECU verus ECM or ECM versus PCM?

ECU versus ECM

ECU stands for engine control unit, while ECM stands for engine control module. Both acronyms and names mean the same thing. They receive data inputs from sensors and use that data to control the engine’s fuel and ignition systems, intake manifold runners, variable valve timing mechanisms, and engine cooling systems.

In vehicles with an ECU or ECM, carmakers often relay on a separate module to control the transmission shifting. The transmission control module (TCM) communicates digitally with the ECU/ECM to determine when to shift.

ECM versus PCM

A powertrain control module (PCM) incorporates all the functions of an ECU/ECM and a TCM, so it controls both the engine and transmission operations in a single unit.

Sensors used by the ECU/ECM

Intake air temperature (ambient air temperature)
Engine coolant temperature
Oxygen sensor data
Knock sensor
Camshaft position sensor
Crankshaft position sensor
EGR position sensor
Manifold runner sensor
Fuel rail pressure sensor

Additional sensors used by the PCM or TCM

Input shaft speed sensor
Output shaft speed sensor
Transmission fluid temperature sensor
Transmission pressure sensor

©, 2021 Rick Muscoplat