An ECM from a 1996 Chevrolet Beretta- 2013-10-24 23-13

A power-train control module, abbreviated PCM, is an automotive component, a control unit, used on

motor vehicle A motor vehicle, also known as motorized vehicle or automotive vehicle, is a self-propelled land vehicle, commonly wheeled, that does not operate on Track (rail transport), rails (such as trains or trams) and is used for the transportation of pe ...

s. It is generally a combined controller consisting of the

engine control unit An engine control unit (ECU), also commonly called an engine control module (ECM), is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance. It does this by re ...

(ECU) and the transmission control unit (TCU). On some cars, such as many Chryslers, there are multiple computers: the PCM, the TCU, and the Body Control Module (BCM), for a total of three separate computers. 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. 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. Early use of the powertrain control module dates back to the late 1970s - official phasing in of the PCM occurred during the early 1980s when used in conjunction with electronic controlled

carburetor A carburetor (also spelled carburettor) is a device used by an internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the venturi tube in the main meteri ...

s and

lockup torque converter A torque converter is a type of fluid coupling that transfers rotating power from a prime mover, like an internal combustion engine, to a rotating driven load. In a vehicle with an automatic transmission, the torque converter connects the power ...

s (at the time conventional 3-speed automatics received lockup converters at the same time overdrives were introduced).

Other names

Engine control unit is also called: * PCM: Power-train control module (Ford/ GM) * ECM: Engine control module * Injection control unit (Peugeot, Citroën, Fiat, Alfa, Lancia) * DME/DDE: Digital Motor Electronics / Digital Diesel Electronics (BMW, Mini) * ECU: Electronic control unit / Engine control unit

Bibliography

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References

{{Reflist Power control Engine technology Fuel injection systems Engine components Onboard computers Auto parts