It depends on the manufacturer. Some OEMs call the Engine Control Unit the ECU while others use the general terminology where all Electronic Control Units are E

It depends on the manufacturer. Some OEMs call the Engine Control Unit the ECU while others use the general terminology where all Electronic Control Units are ECUs and the engine controller is an Electronic Control Unit named the PCM (Powertrain Control Module) or ECM (Engine Control Module). In those cases, there are some strange ECUs... ex. the steering wheel is an ECU, the stereo headunit is an ECU, etc.