Engine Control Module: Description and Operation

Engine Control Module:

Fig. 5 ECM Unit (Showing PROM & CALPAK Locations):

The Electronic Control Module (ECM), located in the passenger compartment, is the control center of the fuel injection system. The ECM continually monitors and processes the input information and generates output commands to the various systems affecting vehicle performance.

A removable calibration unit (PROM) enables the ECM to recognize and adjust for vehicle variations (vehicle weight, axle ratio, etc.). There are specific ECM/PROM combinations for each specific vehicle which are not interchangeable, Fig. 4.

On V6 models, a CALPAK is also installed in the ECM. The CALPAK allows fuel delivery in the case that other parts of the ECM are damaged, Fig. 5.

The ECM also performs the diagnostic function of the fuel injection system. When the ECM senses an operational problem, it will illuminate the "Check Engine" or "Service Engine Soon" light and store the appropriate code(s) to identify the problem area.