Skyhawk L4-121 2.0L Turbo VIN M FI (1987)
Engine Control Module: Description and Operation
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 calibration unit
called the PROM (Programable Read Only Memory) enables the ECM to recognize and adjust for vehicle variations (vehicle weight, axle ratio, etc.).
The CALPAK allows fuel delivery if other parts of the ECM are damaged. The PROM, CALPAK and ESC control module are combined into a single
calibration unit called MEM-CAL. The MEM-CAL includes calibrations for the specific engine/vehicle calibration, as well as the back-up fuel control
circuitry needed to allow engine operation in the event of an ECM failure.
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'' lamp and store the appropriate code(s) to identify the problem area.
