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.
1999 Infiniti QX4FACTORY OEM SERVICE PROCEDURE
Key-In Switch Circuit Check
- Turn ignition switch to LOCK position. Using a voltmeter, backprobe terminal No. 24 (White/Red wire) at Smart Entrance Control Unit (SECU) harness connector. See Figure . When key is in ignition switch, battery voltage should exist. When key is out of ignition switch, zero volts should exist. If voltage is as specified, key-in switch circuit is okay at this time. If voltage is not as specified, go to next step.
- Turn ignition switch to LOCK position. Remove lower steering column cover. Disconnect key-in switch harness connector. Measure resistance between key-in switch terminals (component side). When key is in ignition switch, continuity should exist. When key is out of ignition switch, continuity should not exist. If continuity is not as specified, replace key-in switch. If continuity us as specified, check for the following and repair as necessary:
- Faulty fuse No. 24 (7.5-amp) in instrument panel fuse box.
- Open and/or short in Yellow/Blue wire between instrument panel fuse box and key-in switch.
- Open and/or short in White/Red wire between SECU and key-in switch.
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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