A PCM, or powertrain control module, is an automotive component that acts as a control unit for motor vehicles. It is generally a combined controller consisting of the engine control unit (ECU) and the transmission control unit (TCU) . The PCM manages the engine, transmission, and other systems based on information it receives from various sensors around the vehicle. It is responsible for controlling the powertrain, which includes the engine and transmission, and monitors parameters such as engine speed, coolant temperature, and throttle position. The PCM commonly controls more than 100 factors in a car or truck, and 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.