[[File:An ECM from a 1996 Chevrolet Beretta- 2013-10-24 23-13.jpg|thumbnail|An ECU from a 1996 [[Chevrolet Beretta]].]]
A '''power-train control module''', abbreviated '''PCM''', is an [[automotive industry|automotive]] component, an [[electronic control unit]] (ECU), used on [[motor vehicle]]s. It is generally a combined control unit, consisting of the [[engine control unit]] (ECU) and the [[transmission control unit]]. On some cars, such as many Chrysler'sChryslers, there are multiple computers: the PCM, the Transmission Control Unit, and the Body Control Module, for a total of three separate computers as an example. These automotive computers are generally very reliable. The PCM commonly controls more than 100 factors in a car or truck. There are many hundreds of error codes that can occur, which indicates that some subsection of the car is experiencing a problem. When one of these errors occurs, usually it will turn on the "check engine" light on the dashboard. The PCM is one of potentially several on-board computers, or essentially the "brain" of the engine control system. When the "brain" does not function correctly, neither will the engine or anything else that the microprocessor controls, which may include the charging system, transmission, various emission controls and communications with other on-board control modules. The PCM should be replaced only when it is diagnosed to be defective.
On board Diagnostic (OBD II) diagnostic trouble codes that typically indicate a fault with the power-train control module include:
