The Powertrain Control Module (PCM) and Engine Control Module (ECM) are terms often used interchangeably, but they serve distinct purposes. The PCM oversees not only the engine but also the transmission system, integrating multiple control modules into a unified unit. On the other hand, the ECM focuses solely on engine-related functions, excluding transmission control. How do ECUs, PCMs, and ECMs Work? These control modules receive input from various sensors throughout the vehicle, such as ...