Electronic Control Module

The electronic control module (ECM) is located under the instrument panel and is the control center of the fuel injection system. It constantly monitors information from the various sensors and controls systems affecting vehicle performance. A reference signal of 5 volts is used between the ECM and all sensors.

The control module has 2 parts: The controller (ECM minus PROM), and a separate calibrator or PROM (Programmable Read Only Memory). The PROM is specific to the vehicle, and has information on the vehicle weight, engine, transmission, and axle ratio. This allows the use of the same ECM on many different models of vehicles.