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Home >> Infiniti >> 2002 >> Q45 >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - System & Component Testing - G20 & Q45 >> Computerized Engine Controls >> Engine Control Module (ECM) >> Power & Ground Circuits (G20)
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Power & Ground Circuits (G20)

  1. Start engine. If engine starts, go to step  8. If engine does not start, go to next step.
  2. Turn ignition off and on. Measure voltage between ground and ECM terminal No. 43 (Black/Red wire) by backprobing. See Fig 1 and Fig 2 . If battery voltage exists, go to step  4. If battery voltage does not exist, go to next step.
  3. Check the following:
    • Check for poor connection at White, 24-pin connector F24 terminal No. 6 (Black/Red wire). See Fig 3 and Fig 4 .
    • Check for open or short in Black/Red wire between ECM and fuse No. 25 (10-amp) located in fuse block under left side of instrument panel.

    Repair as necessary.

  4. Turn ignition off. Disconnect ECM harness connector. Check continuity between engine ground and ECM harness connector terminals No. 48, 57, 106 and 108 (Black wires). Continuity should exist. Also, check circuits for short to voltage. If problem is found, repair as necessary. If circuits are okay, go to next step.
  5. Disconnect ECM relay harness connector. See Fig 5. Measure voltage between ground and ECM relay harness connector terminals No. 1 (White/Blue wire) and No. 6 (Red/Black wire). See Figure. If battery voltage exists, go to step  7. If battery voltage does not exist, go to next step.
  6. Check the following:
    • Check fuse No. 35 (15-amp) located in fuse and fusible link box on left side of engine compartment.
    • Check fuse No. 5 (7.5-amp) located in fuse block under left side of instrument panel.
    • Check for poor connection at Super Multiple Junction (SMJ) connector terminal 67K (Red/Black wire). See Fig 6. SMJ connector is located under left side of instrument panel, behind fuse block.
    • Check for open or short between ECM and battery.

    Repair as necessary.

  7. Check continuity of White/Green wire between ECM relay harness connector terminal No. 2 and ECM harness connector terminal No. 31. Also, check circuit for short to ground and short to voltage. If problem is found, repair as necessary. If circuit is okay, go to IGNITION SIGNAL  under IGNITION SYSTEM.
  8. Turn ignition off. Measure voltage between ground and ECM terminal No. 67 (White/Blue wire) by backprobing. See Fig 1 and Fig 2 . If battery voltage exists, go to step  10. If battery voltage does not exist, go to next step.
  9. Check the following:
    • Check for poor connection at White, 24-pin connector F24 terminal No. 4 (White/Blue wire). See Fig 3 and Fig 4 .
    • Check for poor connection at fuse block harness connector M5 terminal 1E (White/Blue wire). See Fig 7. Fuse block is located under left side of instrument panel.
    • Check fuse No. 4 (7.5-amp) located in fuse block.
    • Check for open or short between ECM and fuse.

    Repair as necessary.

  10. Turn ignition on and off. Measure voltage between ground and ECM terminals No. 110 and 112 (both White wires) by backprobing. Battery voltage should exist for a few seconds after ignition is turned off. After a few seconds, voltage should drop to about zero volts. If voltage is as specified, go to step  15. If battery voltage does not exist, go to next step. If battery voltage exists for more than a few seconds, go to step  12.
  11. Disconnect ECM relay harness connector. See Fig 5. Measure voltage between ground and ECM relay harness connector terminal No. 5 (White/Blue wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short between ECM relay and fuse No. 4 (7.5-amp).
  12. Disconnect ECM relay and ECM harness connectors. Check continuity of White wire between ECM relay harness connector terminal No. 3 and ECM harness connector terminals No. 110 and 112. Also, check circuit for short to ground and short to voltage. If problem is found, go to next step. If circuit is okay, go to step  14.
  13. Check the following:
    • Check for poor connection at White, 24-pin connector F24 terminal No. 2 (White wire). See Fig 3 and Fig 4 .
    • Check for open or short between ECM and ECM relay.

    Repair as necessary.

  14. Check ECM relay. See RELAYS & SOLENOIDS . If ECM relay is okay, go next step. If ECM relay is not okay, replace ECM relay.
  15. Turn ignition off. Disconnect ECM harness connector. Check continuity between engine ground and ECM harness connector terminals No. 48, 57, 106 and 108 (Black wires). Continuityshould exist. Also, check circuits for short to voltage. If problem is found, repair as necessary. If circuits are okay, go to next step.
  16. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
Fig 1: Locating ECM Harness Connector (G20)
G00010187Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: Identifying ECM Harness Connector Terminals (G20)
G99E52781Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 3: Locating Engine Control Harness Connectors (G20)
G00025005Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 4: Identifying Connector F24 Terminals (G20)
G00064013Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 5: Locating ECM Relay & Fuel Pump Relay No. 1 (G20)
G00010137Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 6: Identifying Super Multiple Junction Connector Terminals (G20)
G00064001Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 7: Identifying Fuse Block Connectors & Terminals (G20)
G00103753Courtesy of NISSAN MOTOR CO., U.S.A.
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