[[File:An_ECM_from_a_1996_Chevrolet_Beretta-_2013-10-24_23-13.jpg|thumbnail|An ECU from a 1996 [[Chevrolet Beretta]].]]
A '''powertrain 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 moduleunit]] (ECMECU) and the [[transmission control moduleunit] (TCM)]. On some cars, such as many Chryslers, there are multiple computers: the PCM, the Transmission Control ModuleUnit, 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 onboard 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 onboard 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 powertrain control module include:
