ECU unit location

The ECM is the heart of the engine management system

The onboard computer, or Powertrain Control Module (PCM), is the brains of the engine control system, so when the brain is not functioning correctly neither is the engine or anything else that the microprocessor controls - which may include the charging system, transmission, various emission controls and communications with other onboard control modules. Once a diagnosis has been made (and we emphasize the word diagnosis), then and only then should the PCM be replaced.