2003 Infiniti FX45FACTORY OEM SERVICE PROCEDURE

Electrical Load Signal: QX4

  1. Turn ignition switch to ON position. Using voltmeter, measure voltage between ground and ECM terminal 52. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Turn rear window defogger switch to ON position and check voltage. Turn rear window defogger switch to OFF position and check voltage. See ELECTRICAL LOAD TEST (QX4)  table. If voltage readings are as specified, go to next step. If voltage readings are not as specified, go to step  3.
    ELECTRICAL LOAD TEST (QX4)

    System Condition Voltage
    Rear Window Defogger
    On 12
    Off Zero
    Lighting
    On 12
    Off Zero
  2. Turn ignition switch to ON position. Using voltmeter, measure voltage between ground and ECM terminal No. 52. Turn headlight switch to ON position and check voltage. Turn headlight switch to OFF position and check voltage. See ELECTRICAL LOAD TEST (Q45)  table. If voltage readings are as specified, inspection is complete. If voltage readings are not as specified, go to next step.
  3. Start engine. Turn rear window defogger switch to ON position. If rear window heats up, go to next step. If rear window does not heat up, repair rear window defogger system. See appropriate REAR WINDOW DEFOGGERS article in ACCESSORIES & EQUIPMENT.
  4. Turn ignition switch to OFF position. Disconnect ECM harness connector. Disconnect rear window defogger relay. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Using ohmmeter, check continuity between ECM harness connector terminal No. 52 and rear window defogger relay harness connector terminal No. 7. Ensure ohmmeter leads are correctly placed for both test conditions. See Fig 1. Also check harness for short to ground or short to power. If no problem is found, go step  6. If problem is found, go to next step.
    Fig 1: Testing Rear Window Defogger Circuit (QX4)
    G00221710Courtesy of NISSAN MOTOR CO., U.S.A.
  5. Check the following:
    • Check harness connectors E1 and M1.
    • Check harness connectors M33 and F22.
    • Diode M37.
    • Harness for short or open between ECM and rear window defogger relay.

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

  6. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
  7. Start engine. Turn headlight switch to ON position (2nd position). If headlights operate, go to next step. If headlights do not operate, repair headlight system. See appropriate HEADLIGHT SYSTEMS article in ACCESSORIES & EQUIPMENT.
  8. Stop engine. Ensure ignition switch is in OFF position. Disconnect ECM harness connector. Disconnect headlight relay harness connector. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Using ohmmeter, check continuity between ECM harness connector terminal No. 52 and LH headlight relay harness connector terminal No. 5. Ensure ohmmeter leads are correctly placed for both test conditions. See Fig 2. Also check harness for short to ground or short to power. If no problem is found, go to next step. If problem is found, go to step  10.
    Fig 2: Testing Headlight Signal Circuit Continuity (QX4)
    G00221708Courtesy of NISSAN MOTOR CO., U.S.A.
  9. Disconnect Daytime Running Light (DRL) control unit harness connector. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Using ohmmeter, check continuity between ECM harness connector terminal No. 52 and DRL control unit harness connector terminal No. 5. Ensure ohmmeter leads are correctly placed for both test conditions. See Fig 3. Also check harness for short to ground or short to power. If problem is found, go next step. If no problem is found, go to step  11.
    Fig 3: Testing DRL Unit Continuity (QX4)
    G00221709Courtesy of NISSAN MOTOR CO., U.S.A.
  10. Check the following:
    • Harness connectors E1 and M1.
    • Harness connectors M33 and F22.
    • Diode E121.
    • Harness for short or open between ECM and headlamp left side relay or daytime running light control unit.

    Repair as necessary.

  11. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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