1998 Infiniti QX4FACTORY OEM SERVICE PROCEDURE

Fast Idle Control Device (FICD) System Test: Quest

  1. Start engine and warm to operating temperature. Check idle speed. See SPECIFICATIONS article. Adjust idle speed if necessary. See ADJUSTMENTS article. Turn A/C and blower fan switches on. Idle speed should increase. If idle speed does not increase, go to next step. If idle speed increases, system is functioning properly.
  2. Ensure A/C compressor functions normally. If compressor is not functioning, repair A/C system as necessary. If compressor is functioning, go to next step.
  3. Turn ignition off. Disconnect FICD solenoid harness connector. Using DVOM, measure voltage between ground and FICD solenoid harness connector terminal No. 1 (Blue/Yellow wire). Battery voltage should be present. If battery voltage is present, go to next step. If battery voltage is not present, check 10-amp fuse. See WIRING DIAGRAMS article. If fuse is okay, repair open or short in Blue/Yellow wire. Also check Blue wire between fuse and FICD relay, harness connectors and FICD relay. See RELAYS  under RELAYS & SOLENOIDS.
  4. Turn ignition off. Check continuity between ground and FICD solenoid harness connector terminal No. 2 (Black wire). Continuity should exist. If continuity exists, go to next step. If continuity does not exist, repair open Black wire.
  5. Check FICD solenoid. See FAST IDLE CONTROL DEVICE (FICD) SOLENOID . If FICD solenoid is okay, check PCM and harness connector terminals for damage or corrosion. Repair or replace as necessary and go to next step.
  6. Start engine. Using DVOM, measure voltage between PCM harness connector terminal No. 21 (White/Red wire) and ground by backprobing connector. Voltage should be 2.3 volts with A/C and blower fan switch on and ambient air temperature more than 50°F (10°C). Voltage should be approximately battery voltage with A/C off. If voltage is as specified, system is functioning properly. If voltage is not as specified, diagnose fault in A/C system. See A/C-HEATER SYSTEMS article in the AIR CONDITIONING & HEAT section.
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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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