2001 Infiniti Q45 BaseFACTORY OEM SERVICE PROCEDURE

Electrical Load Signal: Q45

  1. Turn ignition off. Disconnect ECM harness connector. See Figure. Turn ignition on. Measure voltage between ground and ECM harness connector terminal No. 79. See Figure. Turn rear window defogger on. Battery voltage should exist. Turn rear window defogger off. Zero volts should exist. If voltage is as specified, go to next step. If voltage is not as specified, go to step  3.
  2. Measure voltage between ground and ECM harness connector terminal No. 72. Turn headlights on. Battery voltage should exist. Turn headlights off. Zero volts should exist. If voltage is as specified, test is complete. If voltage is not as specified, go to step  5.
  3. Check rear window defogger operation. If rear window defogger operates properly, go to next step. If rear window defogger does not operate properly, repair rear window defogger system. See REAR WINDOW DEFOGGERS article in ACCESSORIES & EQUIPMENT.
  4. Turn ignition off. Disconnect rear window defogger relay, located behind left kick panel. Check continuity of Blue/Red wire between rear window defogger relay harness connector terminal No. 5 and ECM harness connector terminal No. 79. Also check circuit for short to ground and short to voltage. Repair as necessary and retest system. If circuit is okay, go to step  8.
  5. Check operation of headlights. If headlights operate properly, go to next step. If headlights do not operate properly, repair headlight system. See appropriate wiring diagram in HEADLIGHT SYSTEMS article in ACCESSORIES & EQUIPMENT.
  6. Remove headlight relay, located in relay box on right side of engine compartment. Check continuity between ECM harness connector terminal No. 72 (Red/Yellow wire) and headlight relay harness connector terminal No. 6 (Blue/White wire). 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.
  7. If vehicle is not equipped with xenon headlights, go to next step. If vehicle is equipped with xenon headlights, remove High Intensity Discharge (HID) relay, located next to headlight relay. Check continuity of Red/Yellow wire between ECM harness connector terminal No. 72 and HID relay harness connector terminal No. 7. 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.
  8. 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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