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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 (Q45)
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Power & Ground Circuits (Q45)

  1. Start engine. If engine starts, go to step  10. If engine does not start, go to next step.
  2. Turn ignition switch to OFF position then ON. Measure voltage between ground and ECM terminal No. 53 (White/Green wire) by backprobing. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If battery voltage exists, go to step  4. If battery voltage does not exist, go to next step.
  3. Check the following:
    • Harness connectors E32 and F32. See Fig 2.
    • Fuse block (J/B) No. 1 connector M1. See Fig 4.
    • Fuse block (J/B) No. 2 connector M143 and E215. See Fig 1.
    • Joint connector-19. See Fig 3.
    • Harness for open or short between ECM and fuse.

    Repair as necessary.

  4. Turn ignition switch to OFF position. Disconnect ECM harness connector. Check continuity between engine ground and ECM harness connector terminals No. 156 and 159. Also check continuity between engine ground and ECM harness connector and terminals No. 165 and 168. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Continuity should exist. Also, check circuits for short to voltage. If problem is found, go to next step. If no problem is found, go to step  6.
  5. Check the following:
    • Check joint connector No. 29.
    • Harness for open or short between ECM and ground.

    Repair as necessary.

  6. Remove ECM relay from fuse block No. 2. See Fig 1. Fuse block No. 2 is located under right side of instrument panel. Measure voltage between ground and ECM relay cavities No. 2 and 5. See Figure. If battery voltage exists, go to step  8. If battery voltage does not exist, go to next step.
  7. Check the following:
    • Check fuse No. 32 (10-amp) located in fuse block No. 2. See Fig 1. Fuse block No. 2 is located under right side of instrument panel.
    • Check fuse No. 53 (20-amp) located in fuse, fusible link and relay block on right side of engine compartment.
    • Check for poor connection at fuse block No. 2 connector E215. See Fig 1.
    • Check for poor connection at fuse, fusible link and relay block connector E3.
    • Check for open or short between ECM relay and battery.

    Repair as necessary.

  8. Check continuity between ECM relay cavity No. 1 and ECM harness connector terminal No. 42. Continuity should exist. Also, check circuit for short to ground and short to voltage. If problem is found, go to next step. If circuit is okay, see IGNITION COIL & POWER TRANSISTOR (Q45)  under IGNITION SIGNAL in IGNITION SYSTEM.
  9. Check the following:
    • Check harness connectors M135 and F105.
    • Check fuse block (J/B) No. 2 connector M143.
    • Check for open or short between ECM relay and ECM.

    Repair as necessary.

  10. Measure voltage between ground and ECM terminals No. 12, 163 and 166 by backprobing. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Turn ignition switch to ON position and then to OFF position. Battery voltage should exist for a few seconds after turning ignition switch to OFF position, 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  13.
  11. Disconnect ECM relay. Check voltage between ground and ECM relay terminal No. 7 by backprobing. Battery voltage should still exist. If voltage exists, go to step  13. If voltage does not exist, go to next step.
  12. Check harness for open or short between ECM relay and 10-amp fuse. Repair open circuit or short to ground or short to power in harness or connectors.
  13. Check harness continuity between ECM and ECM relay specified terminals. See HARNESS CONTINUITY  table.
    HARNESS CONTINUITY

    ECM Terminal No. ECM Relay Terminal No.
    12 3 (Harness Connector F105 Terminal 4T)
    163, 166 6

    Continuity should exist. Repair as necessary. Also check harness for short to ground and short to power. If results are as specified, go to step  16. 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 as necessary.

  15. Check ECM relay. See ECM RELAY  in RELAYS under RELAYS & SOLENOIDS. If ECM relay okay, go to next step. If ECM relay not okay, replace ECM relay.
  16. Turn ignition to OFF position. Disconnect ECM harness connector. Check continuity between engine ground and ECM harness connector terminals No. 156, 159, 165 and 168. Continuity should exist. Also check circuits for short to voltage. If problem is found, go to next step. If no problem is found, go to step  18.
  17. Check the following:
    • Check joint connector No. 29.
    • Check for open or short between ECM and engine ground.

    Repair as necessary. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL article.

  18. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
Fig 1: Identifying Fuse Block No. 2 Connectors, Fuse & Relays (Q45)
G00064026Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: Identifying Main Harness Connector Locations (Q45)
G00103710Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 3: Identifying Joint Connector No. 19 Continuity (Q45)
G00103754Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 4: Identifying Fuse Block No. 1 Connectors, Fuse & Relays (Q45)
G00064027Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 5: Identifying Joint Connector No. 29 Continuity (Q45)
G00103755Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 6: Identifying Super Multiple Junction (SMJ) Connectors F105 & M135 Terminals
G00064025Courtesy of NISSAN MOTOR CO., U.S.A.
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