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Home >> Infiniti >> 2003 >> Q45 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Computerized Engine Controls >> Engine Control Module (ECM) >> Power & Ground Circuits (QX4)
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Power & Ground Circuits (QX4)

  1. Start engine. If engine is running, go to step  9. If engine is not running, go to next step.
  2. Turn ignition switch to OFF position and then ON. Check voltage between ground and ECM terminal No. 43. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Battery voltage should exist. If voltage is as specified, go to step  4. If voltage is not as specified, go to next step.
  3. Check the following:
    • 10-amp fuse.
    • Harness connectors M33 and F22.
    • Fuse block (J/B) connectors E4 and M10.
    • Harness for open or short between ECM and ignition switch.

    Repair or replace components as necessary.

  4. Turn ignition switch to OFF position. Disconnect ECM harness connector. Check harness for continuity between ECM terminals No. 48, 57, 106, 108 and engine ground. See PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Continuity should exist. Also check harness for short to power. If problem is found, repair open circuit or short to power in harness or connectors as necessary. If no problem is found, go to next step.
  5. Check power supply-II. Disconnect ECM relay. See Fig 1. Check voltage between ground and ECM relay terminals No. 1 and 5. Battery voltage should exist. If voltage is as specified, go to step  7. If voltage is not as specified, go to next step.
    Fig 1: Locating ECM Relay (QX4)
    G00220059Courtesy of NISSAN MOTOR CO., U.S.A.
  6. Check the following:
    • 7.5-amp and 10-amp fuses.
    • Harness for open or short between ECM relay and battery.

    Repair open circuit or short to ground or short to power in harness or connectors.

  7. Check harness continuity between ECM terminal No. 26 and ECM relay terminal No. 2. Continuity should exist. Also check harness for short to ground and short to power. If no problem is found, see IGNITION COIL & POWER TRANSISTOR (QX4)  under IGNITION SIGNAL in IGNITION SYSTEM. If problem is found, go to next step.
  8. Check the following:
    • Harness connectors E1 and M1.
    • Harness connectors M32 and F23.
    • Harness for open or short between ECM relay and ECM.

    Repair open circuit or short to ground or short to power in harness or connectors.

  9. Stop engine. Check voltage between ground and ECM terminal No. 67 with CONSULT-II or tester. Battery voltage should exist. If voltage is as specified, go to step  11. If voltage is not as specified, go to next step.
  10. Check the following:
    • Harness connectors E1 and M1.
    • Harness connectors M32 and F23.
    • Harness for open or short between ECM and fuse.

    Repair harness or connectors.

  11. Turn ignition switch to ON position and then OFF. Check voltage between ground and ECM terminals No. 110 and 112. After turning ignition switch to OFF position, battery voltage will exist for a few seconds, then drop to about zero volts. If voltage is as specified, go to step  17. If battery voltage does not exist, go to next step. If battery voltage exists for more than a few seconds, go to step  14.
  12. Check ECM Power supply circuit-IV. Disconnect ECM relay. See Fig 1. Check voltage between ground and ECM relay terminal No. 7. Battery voltage should exist. If voltage is as specified, go to step  14. If voltage is not as specified, go to next step.
  13. Check harness for open or short circuit between ECM relay and 7.5-amp fuse. Repair open circuit or short to ground or short to power in harness or connectors as necessary.
  14. Check voltage between ground and ECM terminal No. 12. Battery voltage should exist. If voltage is as specified, go to step  16. If voltage is not as specified, go to next step.
  15. Check the following:
    • Harness connectors E1 and M1.
    • Harness connectors M94 and F27.
    • Harness for open or short between ECM and fuse.

    Repair harness or connectors.

  16. Check harness continuity between ECM relay terminal No. 6 and ECM terminals No. 110 and 112. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Continuity should exist. Also check harness for short to ground and short to power. If no problem is found, go to step  18. If problem is found, go to next step.
  17. Check the following:
    • Harness connectors E1 and M1.
    • Harness connectors M32 and F23.
    • Harness for open or short between ECM and ECM relay.

    Repair open circuit of short to ground or short to power in harness or connectors.

  18. Apply 12 volts between ECM relay terminals No. 1 and 2. See Fig 2. Check continuity between relay terminals No. 3 and 5, and terminals No. 6 and 7. Continuity should exist. If continuity is as specified, go to next step. If continuity is not as specified, replace ECM relay.
    Fig 2: Identifying ECM Relay Terminals (M45 & QX4)
    G00220060Courtesy of NISSAN MOTOR CO., U.S.A.
  19. Turn ignition switch to OFF position. Disconnect ECM harness connector. Check harness continuity between engine ground and ECM terminals No. 48, 57, 106 and 108. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Continuity should exist. Also check harness for short to power. If no problem is found, go to next step. If problem is found, repair open circuit or short to power in harness or connectors.
  20. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. If results are as specified, inspection is complete.
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