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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. If fuel pump operates, go to step 5). If fuel pump does not operate, check ECM keyed (ignition) power circuit. See ECM POWER SOURCE CIRCUIT (IGNITION KEYED)  under COMPUTERIZED ENGINE CONTROLS. Repair as necessary.
  2. Check circuit opening relay. See RELAYS under MODULES, MOTORS, RELAYS & SOLENOIDS. Replace circuit opening relay as necessary. If relay is okay, access ECM connectors behind glove compartment. Backprobing connector, measure voltage between chassis ground and terminal No. 18 (Green/Red wire) at ECM E8 connector. See Figure.
  3. 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.
  4. 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.
  5. Check circuit opening relay. See RELAYS under MODULES, MOTORS, RELAYS & SOLENOIDS. Replace circuit opening relay as necessary. If relay is okay, while cranking engine, measure voltage between chassis ground and terminal No. 3 (Black/White wire) of socket where circuit opening relay was installed (corresponding terminal on relay is ST).
  6. If battery voltage is present, repair open circuit between chassis ground and terminal No. 6 (White/Black wire) of socket where circuit opening relay was installed. If battery voltage is not present, check starter signal circuit. See DTC P1500 - STARTER SIGNAL CIRCUIT MALFUNCTION in TESTS W/CODES article. Repair as necessary.
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