The Engine Control Module (ECM) is the computer responsible for controlling the engine. The ECM communicates with other vehicle control units via a communication bus.

What is the Electronic Control Module? Also referred to as an engine control unit (ECU) or engine control module, it oversees the electrical system of the car, but focuses on engine performance.

Consumer Reports explains what the check engine light means and what to do when you see it: how to tell if your car has a loose gas cap—or a serious engine problem.