LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Infiniti >> 2005 >> QX56 AWD >> Repair and Diagnosis >> Engine Performance >> Engine Control System >> Basic Service Procedure >> Idle Mixture Ratio Adjustment >> Detailed Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Detailed Procedure

  1. INSPECTION START 
    1. Check service records for any recent repairs that may indicate a related malfunction, or a current need for scheduled maintenance.
    2. Open engine hood and check the following:
      • Harness connectors for improper connections
      • Wiring harness for improper connections, pinches and cut
      • Vacuum hoses for splits, kinks and improper connections
      • Hoses and ducts for leaks
      • Air cleaner clogging
      • Gasket
    3. Confirm that electrical or mechanical loads are not applied.
      Fig 1: Checking Wiring Harness For Improper Connections, Pinches And Cut
      G02384794Courtesy of NISSAN MOTOR CO., U.S.A.
      • Head lamp switch is OFF.
      • Air conditioner switch is OFF.
      • Rear window defogger switch is OFF.
      • Steering wheel is in the straight-ahead position, etc.
    4. Start engine and warm it up until engine coolant temperature indicator points the middle of gauge.

      Ensure engine stays below 1,000 RPM.

      Fig 2: Identifying Temperature Gauge
      G02384795Courtesy of NISSAN MOTOR CO., U.S.A.
    5. Run engine at about 2,000 RPM for about 2 minutes under no load.
    6. Make sure that no DTC is displayed with CONSULT-II or GST.

    OK or NG 

    1. OK: GO TO  3.
    2. NG: GO TO 2.
    Fig 3: Identifying Reading On RPM Meter
    G02384796Courtesy of NISSAN MOTOR CO., U.S.A.
  2. REPAIR OR REPLACE 

    Repair or replace components as necessary according to corresponding Diagnostic Procedure.

    1. GO TO 3.
  3. CHECK TARGET IDLE SPEED 

    With CONSULT-II 

    1. Run engine at about 2,000 RPM for about 2 minutes under no load.
    2. Rev engine (2,000 to 3,000 RPM) 2 or 3 times under no load, then run engine at idle speed for about 1 minute.
      Fig 4: Identifying Reading On RPM Meter
      G02384797Courtesy of NISSAN MOTOR CO., U.S.A.
    3. Read idle speed in "DATA MONITOR" mode with CONSULT-II. Refer to "IDLE SPEED ".
      1. 650 +/- 50 RPM (in P or N position) 
      Fig 5: CONSULT-II Display - DATA MONITOR
      G02384798Courtesy of NISSAN MOTOR CO., U.S.A.

    Without CONSULT-II 

    1. Run engine at about 2,000 RPM for about 2 minutes under no load.
    2. Rev engine (2,000 to 3,000 RPM) 2 or 3 times under no load, then run engine at idle speed for about 1 minute.
    3. Check idle speed.

      Refer to "IDLE SPEED ".

      1. 650 +/- 50 RPM (in P or N position) 

    OK or NG 

    1. OK: GO TO  10 0.
    2. NG: GO TO 4.
  4. PERFORM ACCELERATOR PEDAL RELEASED POSITION LEARNING 
    1. Stop engine.
    2. Perform "ACCELERATOR PEDAL RELEASED POSITION LEARNING ".
    1. GO TO 5.
  5. PERFORM THROTTLE VALVE CLOSED POSITION LEARNING 

    Perform "THROTTLE VALVE CLOSED POSITION LEARNING ".

    1. GO TO 6.
  6. PERFORM IDLE AIR VOLUME LEARNING 

    Perform "IDLE AIR VOLUME LEARNING ".

    Is Idle Air Volume Learning carried out successfully? 

    Yes or No 

    1. Yes: GO TO 7.
    2. No:
      1. Follow the instruction of Idle Air Volume Learning.
      2. GO TO  4.
  7. CHECK TARGET IDLE SPEED AGAIN 

    With CONSULT-II 

    1. Start engine and warm it up to normal operating temperature.
    2. Read idle speed in "DATA MONITOR" mode with CONSULT-II.

      Refer to "IDLE SPEED ".

      1. 650+/- 50 RPM (in P or N position) 

    Without CONSULT-II 

    1. Start engine and warm it up to normal operating temperature.
    2. Check idle speed.

      Refer to "IDLE SPEED ".

      1. 650 +/- 50 RPM (in P or N position) 

    OK or NG 

    1. OK: GO TO  3.
    2. NG: GO TO 8.
  8. DETECT MALFUNCTIONING PART 

    Check the following.

    OK or NG 

    1. OK: GO TO 9.
    2. NG:
      1. Repair or replace.
      2. GO TO  4.
  9. CHECK ECM FUNCTION 
    1. Substitute another known-good ECM to check ECM function. (ECM may be the cause of an incident, but this is a rare case.)
    2. Perform initialization of IVIS (NATS) system and registration of all IVIS (NATS) ignition key IDs. Refer to "ECM RE-COMMUNICATING FUNCTION ".
    1. GO TO  4.
  10. CHECK IGNITION TIMING 
    1. Run engine at idle.
    2. Check ignition timing with a timing light.

      Refer to "IGNITION TIMING ".

      1. 15 +/- 5° BTDC (in P or N position) 

    OK or NG 

    1. OK (With CONSULT-II): GO TO  19.
    2. OK (With GST): GO TO  20.
    3. NG: GO TO 11.
    Fig 6: Checking Ignition Timing
    G02384799Courtesy of NISSAN MOTOR CO., U.S.A.
  11. PERFORM ACCELERATOR PEDAL RELEASED POSITION LEARNING 
    1. Stop engine.
    2. Perform "ACCELERATOR PEDAL RELEASED POSITION LEARNING ".
    1. GO TO 12.
  12. PERFORM THROTTLE VALVE CLOSED POSITION LEARNING 

    Perform "THROTTLE VALVE CLOSED POSITION LEARNING ".

    1. GO TO 13.
  13. PERFORM IDLE AIR VOLUME LEARNING 

    Perform "IDLE AIR VOLUME LEARNING ".

    Is Idle Air Volume Learning carried out successfully? 

    Yes or No 

    1. Yes: GO TO 14.
    2. No:
      1. Follow the instruction of Idle Air Volume Learning.
      2. GO TO  4.
  14. CHECK TARGET IDLE SPEED AGAIN 

    With CONSULT-II 

    1. Start engine and warm it up to normal operating temperature.
    2. Read idle speed in "DATA MONITOR" mode with CONSULT-II.

      Refer to "IDLE SPEED ".

      1. 650 +/- 50 RPM (in P or N position) 

    Without CONSULT-II 

    1. Start engine and warm it up to normal operating temperature.
    2. Check idle speed.

      Refer to "IDLE SPEED ".

      1. 650 +/- 50 RPM (in P or N position) 

    OK or NG 

    1. OK: GO TO 15.
    2. NG: GO TO  17.
  15. CHECK IGNITION TIMING AGAIN 
    1. Run engine at idle.
    2. Check ignition timing with a timing light.

      Refer to "IGNITION TIMING ".

      1. 15 +/- 5° BTDC (in P or N position) 

    OK or NG 

    1. OK (With CONSULT-II): GO TO 19.
    2. OK (Without CONSULT-II): GO TO 20.
    3. NG: GO TO 16.
    Fig 7: Checking Ignition Timing
    G02384800Courtesy of NISSAN MOTOR CO., U.S.A.
  16. CHECK TIMING CHAIN INSTALLATION 

    Check timing chain installation. Refer to "TIMING CHAIN ".

    OK or NG 

    1. OK: GO TO 17.
    2. NG:
      1. Repair the timing chain installation.
      2. GO TO  4.
  17. DETECT MALFUNCTIONING PART 

    Check the following.

    OK or NG 

    1. OK: GO TO 18.
    2. NG:
      1. Repair or replace.
      2. GO TO  4.
  18. CHECK ECM FUNCTION 
    1. Substitute another known-good ECM to check ECM function. (ECM may be the cause of an incident, but this is a rare case.)
    2. Perform initialization of IVIS (NATS) system and registration of all IVIS (NATS) ignition key IDs. Refer to "ECM RE-COMMUNICATING FUNCTION ".
    1. GO TO  4.
  19. CHECK AIR FUEL RATIO (A/F) SENSOR 1 FUNCTION 

    With CONSULT-II 

    1. Turn ignition switch OFF and wait at a least 10 seconds.
    2. Start engine and warm it up to normal operating temperature.
    3. Drive the vehicle at a speed of 80 km/h (50 MPH) for a few minutes in D position.
      NOTE: Keep the accelerator pedal as steady as possible during the cruising.
    4. Release the accelerator pedal fully until the vehicle speed decreases to 50 km/h (30 MPH).
      NOTE: Never apply brake during releasing the accelerator pedal.
    5. Repeat steps 3 to 4 for 5 times.
    6. Stop the vehicle and connect CONSULT-II to the vehicle.
    7. Make sure that no (1st trip) DTC is displayed in "SELF-DIAG RESULT" mode.

    OK or NG 

    1. OK: INSPECTION END 
    2. NG: GO TO  21
  20. CHECK AIR FUEL RATIO (A/F) SENSOR 1 FUNCTION 

    With GST 

    1. Turn ignition switch OFF and wait at a least 10 seconds.
    2. Start engine and warm it up to normal operating temperature.
    3. Drive the vehicle at a speed of 80 km/h (50 MPH) for a few minutes in D position.
      NOTE: Keep the accelerator pedal as steady as possible during the cruising.
    4. Release the accelerator pedal fully until the vehicle speed decreases to 50 km/h (30 MPH).
      NOTE: Never apply brake during releasing the accelerator pedal.
    5. Repeat steps 3 to 4 for 5 times.
    6. Stop the vehicle and connect GST to the vehicle.
    7. Make sure that no (1st trip) DTC is displayed.

    OK or NG 

    1. OK: INSPECTION END 
    2. NG: GO TO 21
  21. CHECK AIR FUEL RATIO (A/F) SENSOR 1 HARNESS 
    1. Turn ignition switch OFF and disconnect battery ground cable.
    2. Disconnect ECM harness connector.
    3. Disconnect A/F sensor 1 harness connector.
    4. Check harness continuity between the following terminals. Refer to "WIRING DIAGRAM ".
      Fig 8: A/F SENSOR AND ECM TERMINALS
      G02384801Courtesy of NISSAN MOTOR CO., U.S.A.
      1. Continuity should exist. 
    5. Also check harness for short to ground and short to power.

    OK or NG 

    1. OK: GO TO 22.
    2. NG:
      1. Repair open circuit or short to ground or short to power in harness or connectors.
      2. GO TO  4.
  22. PERFORM ACCELERATOR PEDAL RELEASED POSITION LEARNING 
    1. Reconnect ECM harness connector.
    2. Perform "ACCELERATOR PEDAL RELEASED POSITION LEARNING ".
    1. GO TO 23.
  23. PERFORM THROTTLE VALVE CLOSED POSITION LEARNING 

    Perform "THROTTLE VALVE CLOSED POSITION LEARNING ".

    1. GO TO 24.
  24. PERFORM IDLE AIR VOLUME LEARNING 

    Refer to "IDLE AIR VOLUME LEARNING ".

    Is Idle Air Volume Learning carried out successfully? 

    Yes or No 

    1. Yes (With CONSULT-II): GO TO 25.
    2. Yes (Without CONSULT-II): GO TO  26.
    3. No:
      1. Follow the instruction of Idle Air Volume Learning.
      2. GO TO  4.
  25. CHECK CO% 

    With CONSULT-II 

    1. Start engine and warm it up until engine coolant temperature indicator points the middle of gauge.
    2. Turn ignition switch OFF, wait at least 10 seconds and then turn ON.
    3. Select "ENG COOLANT TEMP" in "ACTIVE TEST" mode.
    4. Set "ENG COOLANT TEMP" to 5°C (41 °F) by touching "DOWN" and "Qd"
    5. Start engine and rev it (2,000 to 3,000 RPM) two or three times under no load, then run engine at idle speed.
    6. Check CO%.
      1. Idle CO: 3 - 11% and engine runs smoothly. 

    OK or NG 

    1. OK: GO TO  28.
    2. NG: GO TO  27.
    Fig 9: CONSULT-II Display - ACTIVE TEST
    G02384802Courtesy of NISSAN MOTOR CO., U.S.A.
  26. CHECK CO% 

    Without CONSULT-II 

    1. Start engine and warm it up until engine coolant temperature indicator points to the middle of gauge.
    2. Turn ignition switch OFF.
    3. Disconnect engine coolant temperature sensor harness connector.
    4. Connect a resistor (4.4 kΩ) between terminals of engine coolant temperature sensor harness connector.
    5. Start engine and rev it (2,000 to 3,000 RPM) two or three times

      under no load, then run engine at idle speed.

    6. Check CO%.
      1. Idle CO: 3 - 11% and engine runs smoothly. 
    7. After checking CO%, turn ignition switch OFF, disconnect the resistor from the terminals of engine coolant temperature sensor harness connector, and then connect engine coolant temperature sensor harness connector to engine coolant temperature sensor.
      Fig 10: Identifying Engine Coolant Temperature Sensor Harness Connector
      G02384803Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    1. OK: GO TO  28.
    2. NG: GO TO 27.
  27. RECONNECT AIR FUEL RATIO (A/F) SENSOR 1 HARNESS CONNECTOR 
    1. Turn ignition switch OFF.
    2. Reconnect A/F sensor 1 harness connector.
    1. GO TO 31.
  28. REPLACE AIR FUEL RATIO (A/F) SENSOR 1 
    1. Stop engine.
    2. Replace A/F sensor 1 on the malfunctioning bank.

    With CONSULT-II: GO TO 29.

    With GST: GO TO  30.

  29. CHECK AIR FUEL RATIO (A/F) SENSOR 1 FUNCTION 

    With CONSULT-II 

    1. Turn ignition switch OFF and wait at a least 10 seconds.
    2. Start engine and warm it up to normal operating temperature.
    3. Drive the vehicle at a speed of 80 km/h (50 MPH) for a few minutes in D position.
      NOTE: Keep the accelerator pedal as steady as possible during the cruising.
    4. Release the accelerator pedal fully until the vehicle speed decreases to 50 km/h (30 MPH).
      NOTE: Never apply brake during releasing the accelerator pedal.
    5. Repeat steps 3 to 4 for 5 times.
    6. Stop the vehicle and connect CONSULT-II to the vehicle.
    7. Make sure that no (1st trip) DTC is displayed in "SELF-DIAG RESULTS" mode.

    OK or NG 

    1. OK: GO TO  4.
    2. NG: GO TO  31.
  30. CHECK AIR FUEL RATIO (A/F) SENSOR 1 FUNCTION 

    With GST 

    1. Turn ignition switch OFF and wait at a least 10 seconds.
    2. Start engine and warm it up to normal operating temperature.
    3. Drive the vehicle at a speed of 80 km/h (50 MPH) for a few minutes in D position.
      NOTE: Keep the accelerator pedal as steady as possible during the cruising.
    4. Release the accelerator pedal fully until the vehicle speed decreases to 50 km/h (30 MPH).
      NOTE: Never apply brake during releasing the accelerator pedal.
    5. Repeat steps 3 to 4 for 5 times.
    6. Stop the vehicle and connect GST to the vehicle.
    7. Make sure that no (1st trip) DTC is displayed.

    OK or NG 

    1. OK: GO TO  4.
    2. NG: GO TO 31.
  31. DETECT MALFUNCTIONING PART 

    Check the following.

    OK or NG 

    1. OK: GO TO  33.
    2. NG:
      1. Repair or replace.
      2. GO TO 32.
  32. ERASE UNNECESSARY DTC 

    After this inspection, unnecessary DTC might be displayed.

    Erase the stored memory in ECM and TCM. Refer to "HOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFORMATION " and "OBD-II DIAGNOSTIC TROUBLE CODE (DTC) ".

    1. GO TO 4.
  33. CHECK ECM FUNCTION 
    1. Substitute another known-good ECM to check ECM function. (ECM may be the cause of an incident, but this is a rare case.)
    2. Perform initialization of IVIS (NATS) system and registration of all IVIS (NATS) ignition key IDs. Refer to "ECM RE-COMMUNICATING FUNCTION ".
    1. GO TO  4.