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Home >> Infiniti >> 2001 >> Q45 Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> 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  6. If engine does not start, go to next step.
  2. Turn ignition off and on. Measure voltage between ground and ECM terminal No. 43 by backprobing. See Fig 1 and Fig 2 . If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit and retest system. See WIRING DIAGRAMS article.
  3. 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). Also check circuits for short to voltage. Repair as necessary and retest system. If ground circuits are okay, go to next step.
  4. Disconnect ECM relay harness connector. See Fig 3. Measure voltage between ground and ECM relay harness connector terminals No. 1 (White/Blue wire) and No. 6 (Red/Black wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit and retest system. See WIRING DIAGRAMS article.
  5. 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. Repair as necessary and retest system. If circuit is okay, go to next step.
  6. Turn ignition off. Measure voltage between ground and ECM terminal No. 67 by backprobing. See Fig 1 and Fig 2 . If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit and retest system. See WIRING DIAGRAMS article.
  7. Turn ignition on and off. Measure voltage between ground and ECM terminals No. 110 and 112 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  11. If battery voltage does not exist, go to next step. If battery voltage exists for more than a few seconds, go to step  9.
  8. Disconnect ECM relay harness connector. See Fig 3. Measure voltage between ground and ECM relay harness connector terminal No. 5 (White/Blue wires). If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit and retest system. See WIRING DIAGRAMS article.
  9. 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. Repair circuit as necessary and retest system. If circuit is okay, go to next step.
  10. Check ECM relay. See RELAYS & SOLENOIDS . Replace, if necessary and retest system. If ECM relay is okay, go next step.
  11. 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). Also check circuits for short to voltage. Repair as necessary and retest system. If ground circuits are okay, go to next step.
  12. 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 ECM Relay & Fuel Pump Relay No. 1 (G20)
G00010137Courtesy of NISSAN MOTOR CO., U.S.A.
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