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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 (M45)
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Power & Ground Circuits (M45)

  1. Start engine. If engine is running, go to step  10. If engine is not running, go to next step.
  2. Turn ignition switch to OFF position and then ON. Check voltage between ECM terminal No. 53 and ground. 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:
    • Harness connectors E33 and F33.
    • Fuse block (J/B) No. 1 connector M1.
    • Fuse block (J/B) No. 2 connectors M143 and E215.
    • Joint connector-19.
    • 15-amp fuse.
    • Harness for open or short between ECM and fuse.

    Repair harness or connectors as needed.

  4. Turn ignition switch to OFF position. Disconnect ECM harness connector. Check harness continuity between ECM harness connector terminals No. 156, 159, 165, 168 and engine ground. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Continuity should exist. Also check harness for short to power. If continuity does not exist, go to next step. If continuity exists, go to step  6,
  5. Check the following:
    • Joint connector-29.
    • Harness for open or short between ECM and ground.

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

  6. Disconnect ECM relay. See Fig 1. Check voltage between ECM relay terminals No. 2, 5 and ground. Battery voltage should exist. If voltage is as specified, go to step  8. If voltage is not as specified, go to next step.
    Fig 1: Locating ECM Relay (M45)
    G00220061Courtesy of NISSAN MOTOR CO., U.S.A.
  7. Check the following:
    • 10-amp fuse.
    • 20-amp fuse.
    • Fuse block (J/B) No. 2 connector E215.
    • Fuse, fusible link and relay block (J/B) connector E3.
    • 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.

  8. Check harness continuity between ECM terminal No. 42 and ECM relay terminal No. 1. 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 results are as specified, see IGNITION COIL & POWER TRANSISTOR (M45)  under IGNITION SIGNAL in IGNITION SYSTEM. If results are not as specified, go to next step.
  9. Check the following:
    • Harness connectors M135 and F105.
    • Fuse block (J/B) No. 2 connector M143.
    • 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.

  10. Turn ignition switch to ON position and then OFF. Check voltage between ECM terminals No. 12, 163, 166 and ground. After turning ignition switch to OFF position, battery voltage will exist for a few seconds, then will drop to zero volts. If as specified, go to step  16. If battery voltage does not exist, go to next step. If battery voltage exists for more than a few seconds, go to step  13.
  11. Disconnect ECM relay. Check voltage between ECM relay terminal No. 7 and ground. See Fig 1. Battery voltage should exist. If voltage is as specified, go to step  13. If voltage is not as specified, go to next step.
  12. Check the harness for open or short between ECM relay and 10-amp fuse. Repair open circuit or short to ground of short to power in harness or connectors.
  13. Check harness continuity between ECM terminals and ECM relay terminals. See HARNESS CONTINUITY  table. 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 results are as specified, go to step  15. If results are not as specified, go to next step.
  14. Check the following:
    • Harness connectors M135 and F105.
    • Fuse block (J/B) No. 2 connector M143.
    • Harness for open or short between ECM and ECM relay.

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

  15. Check ECM relay.See ECM RELAY  under RELAYS in RELAYS & SOLENOIDS. See Figure. Replace ECM relay if needed. If relay is okay, go to next step.
  16. Turn ignition switch to OFF position. Disconnect ECM harness connector. Check harness continuity between ECM harness connector terminals No. 156, 159, 165, 168 and engine ground. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Continuity should exist. Also check harness for short to power. If results are as specified, go to step  18. If results are not as specified, go to next step.
  17. Check the following:
    • Joint connector-29.
    • Harness for open or short between ECM and ground.

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

  18. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. If results of testing are as specified, inspection is complete.
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