ENGINE CONTROL MODULE UNIT

A Mercedes-Benz's engine control module (ECM), also known as an engine control unit (ECU), monitors and manages the engine's performance: 

What it does
The ECM monitors sensors and adjusts the ignition timing, fuel injection, and other engine functions to improve fuel efficiency and reduce emissions. 

What it controls
The ECM controls various subsystems of the engine, including the fuel injection and ignition systems. 

What it's also responsible for
In addition to the engine, the ECM also monitors and controls other vehicle functions, such as braking and steering