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Home >> Isuzu >> 1994 >> Trooper SE >> Repair and Diagnosis (Single Page) >> Engine Performance >> Theory and Operation >> Engine Controls - Theory & Operation - EFI >> Computerized Engine Controls >> Control Unit

Control Unit

ECM is located under instrument panel, right of steering column.

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. Vehicles with 3.1L engine use an ECM, a separate Programmable Read Only Memory (PROM) calibrator and a Electronic Erasable Programmable Read Only Memory (EEPROM).

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

NOTE: Components are grouped into 2 categories. The first category covers INPUT DEVICES, which control or produce voltage signals monitored by the control unit. The second category covers OUTPUT SIGNALS, which are components controlled by the control unit.
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