An engine control module, or ECM, is a small computer that controls engine function. Also referred to as an engine control unit (ECU) or a powertrain control module (PCM), this electronic device receives and processes data from an array of sensors in and on your engine.
In fact, the ECM receives information from nearly every system in your vehicle - the transmission, traction control, anti-lock brakes, starting and charging, and more. It adjusts the amount of air and fuel that enters the combustion chambers. It controls the timing of the spark plugs. It talks to the anti-theft system to confirm that the right key is being used in the ignition so that your vehicle cannot be easily stolen. The ECM even communicates with other modules, such as the body control module (BCM). It then uses that data to calculate and control dozens of operations to ensure that your vehicle operates properly at peak power and efficiency.
When there is a problem with a vehicle system (such as a bad oxygen sensor, or engine overheating), the ECM stores a diagnostic trouble code that can be accessed and interpreted by a mechanic, and it turns on the check engine light to let you know there is a problem.
The main job of the engine control module is to ensure proper operation of your engine. And since the ECM is directly responsible for overseeing most of the electrical activity, if it malfunctions, your engine will likely show signs that it is in trouble. Many of the signs of a bad ECM mirror other issues. Still, your vehicle might need a new ECM if you notice any of the following:
The engine control module is located in different places depending on the vehicle make and model. It might be found in a housing inside the engine compartment, underneath a seat, behind a kick panel, or underneath the floorboard. To replace the engine control module, a technician must first locate the device and then perform the following general tasks: