Port Fuel Injection

The Electronic Control Module (ECM), located in the passenger compartment, is the control center for 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 called the PROM (Programable Read Only Memory) 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.
A CALPAK is also installed in the ECM. The CALPAK allows fuel delivery if other parts of the ECM are damaged.