Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1998 Infiniti QX4FACTORY OEM SERVICE PROCEDURE
Electrical Load: Maxima
- Turn ignition off. Disconnect PCM harness connector. Turn ignition on. Measure voltage between ground and PCM harness connector terminal No. 79 (Red/White wire). See Figure. With rear window defogger on, battery voltage should exist. With rear window defogger off, zero volts should exist. If voltage is not as specified, go to next step. If voltage is as specified, system is functioning properly.
- Turn ignition off. Check rear window defogger for correct operation. See appropriate REAR WINDOW DEFOGGERS article in the ACCESSORIES/SAFETY EQUIP section. If rear window defogger operates normally, go to next step. If rear window defogger does not operate normally, repair as necessary.
- Disconnect rear window defogger relay. Check continuity between PCM terminal No. 79 (Red/White wire) and rear window defogger relay harness connector terminal No. 5 (Blue/Red wire) and terminal No. 7 (Blue/Yellow wire). See Figure. Continuity should exist. If continuity exists, go to next step. If continuity does not exist, check and repair appropriate wire between PCM and relay. Also check for blown fuses and/or circuit harness connector terminals for pushed-out, bent, damaged or corroded terminals. Repair harness or connectors as necessary. See WIRING DIAGRAMS article.
Factory Service Tools
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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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