Engine Control Module: Description and Operation

Engine control module (ECM) / powertrain control module (PCM)
ECM (PCM) (1) is installed to the underside of the instrument panel at the passenger's seat side. ECM is a precision unit consisting of microcomputer, A/D (analog / digital) converter, I/O (input/output) unit, etc.

It is an essential part of the electronic control system, for its functions include not only such a major function as to control fuel injector, idle air control valve, fuel pump relay, etc. but also on-board diagnostic system (self-diagnosis function) and fail-safe function (Refer to "On-Board Diagnostic System Description (for Engines)".)