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Fuel Pump Control Circuit

CAUTION: If ECM replacement is instructed, always ensure ECM harness connector and ground circuit are okay. If either are suspect, repair as necessary and repeat testing to confirm ECM malfunction.
  1. Check fuel pump operation. See FUEL PUMP OPERATION (USING LEXUS SCAN TOOL)  or FUEL PUMP OPERATION (USING BATTERY VOLTAGE) . If fuel pump does not operate, go to next step. If fuel pump operates, check starter signal circuit. See STARTER SIGNAL CIRCUIT  under COMPUTERIZED ENGINE CONTROLS. Repair as necessary.
  2. Check ECM power source circuit. See ECM POWER SOURCE CIRCUIT (IGNITION KEYED)  under COMPUTERIZED ENGINE CONTROLS. Repair as necessary. If circuit is okay, go to next step.
  3. Check circuit opening relay. See RELAYS  under RELAYS & SOLENOIDS. Replace circuit opening relay as necessary. If relay is okay, access ECM connectors behind glove compartment. Turn ignition on. On ES300, backprobing connector, measure voltage between chassis ground and terminal No. 3 (Green/Red wire) at ECM E7 connector. See Figure. On RX300, backprobing connector, measure voltage between chassis ground and terminal No. 3 (Blue/Yellow wire) at ECM E5 connector. See Figure.
  4. On all models, if battery voltage is not present, check for an open circuit in wiring harness between EFI main relay and circuit opening relay or between opening relay and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Replace as necessary. If battery voltage is present, go to next step.
  5. Check fuel pump. See FUEL PUMP RESISTANCE . Replace fuel pump as necessary. If fuel pump is okay, check for an open circuit in wiring harness between circuit opening relay and fuel pump or between fuel pump and ground. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest.
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