Engine Control Module Description: Notes

The engine control module (ECM) is located behind the passenger kick panel. The ECM is responsible for the control of all engine functions that affect vehicle operation and performance. The ECM also performs the diagnostic functions of the engine control systems. The ECM is responsible for the OBD II diagnostic tests of the emission related systems.

The ECM supplies either 5 or 12 volts to the engine control sensors or switches. These supply circuits are buffered and have a high internal circuit resistance that requires the use of a digital voltmeter with a 10 megaohm input impedance. The ECM controls most components with an electronic switch that completes a ground circuit when commanded ON. The electronic switch is commonly referred to as an output driver. This control module uses a device called a quad-driver, that operates several components simultaneously.

There are no serviceable parts in the ECM. The calibrations are stored in the ECM in either a programmable read only memory (PROM) or an erasable programmable read only memory (EPROM).