ECM is an acronym for Engine Control Module. The ECM is sometimes referred to as a ECU (Engine Control Unit) also. The ECM is responsible for monitoring all the incoming data from sensors and driver inputs, such as throttle position, and making the correct outputs to injectors, fuel pumps, emission control devices, and everything else that goes into running a modern internal combustion engine. The ECM is constantly making adjustment to keep the engine running its best. We have it to thanks for the easy starts and clean running of modern engines.