<P> A power - train control module, abbreviated PCM, is an automotive component, a control unit, used on motor vehicles . It is generally a combined control unit, consisting of the engine control unit (ECU) and the transmission control unit (TCU). On some cars, such as many Chryslers, 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 . </P> <P> The primary inputs to the PCM come from many sensors, of different types, that are spread around the car . Most of them are oriented toward engine management and performance . These sensors fail at a much higher rate than any of the computers do . </P>

What does pcm stand for on a vehicle