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Home >> Lexus >> 2003 >> ES 300 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Fuel Systems >> Fuel Delivery >> Fuel Pump Control Circuit (RX300)
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Fuel Pump Control Circuit (RX300)

  1. Check fuel pump operation. See FUEL SYSTEM under BASIC DIAGNOSTIC PROCEDURES. 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 ON)  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. 10 (Green/Red wire) at ECM E6 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 ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. 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 ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If wiring is okay, replace ECM and retest.
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