Control Unit: ECM

ECM analyzes all electrical data signals from input devices to control fuel injection, ignition and emissions. ECM includes a back-up fail-safe control system. If a malfunction develops in ECM microcomputer, back-up control system will maintain necessary engine functions to permit operation of vehicle.

PROM is factory-programmed engine calibration data, which modifies ECM for specific transmission, engine, emission, vehicle weight and rear axle ratio application. EEPROM (Electronically Erasable Programmable Read Only Memory) provides fuel delivery back-up so engine runs in case of PROM or ECM failure. Anytime ECM is replaced, install original PROM and/or EEPROM into replacement ECM. If battery voltage is removed, PROM and EEPROM information is retained.