LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Infiniti >> 2004 >> QX56 RWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System >> DTC P2138: App Sensor >> Diagnostic Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnostic Procedure

  1. CHECK GROUND CONNECTIONS 
    1. Turn ignition switch OFF.
    2. Loosen and retighten ground three screws on the body.
      Fig 1: Checking Ground Connections
      G02691893Courtesy of NISSAN MOTOR CO., U.S.A.

    Refer to GROUND INSPECTION .

    OK or NG

    OK: GO TO 2.

    NG: Repair or replace ground connections.

  2. CHECK APP SENSOR POWER SUPPLY CIRCUIT 
    1. Disconnect accelerator pedal position (APP) sensor harness connector.
    2. Turn ignition switch ON.
      Fig 2: Checking APP Sensor Power Supply Circuit (1 Of 2)
      G02691894Courtesy of NISSAN MOTOR CO., U.S.A.
    3. Check voltage between APP sensor terminals 6, 7 and ground with CONSULT-II or tester.

      Voltage: Approximately 5V 

    OK or NG

    OK: GO TO  7.

    NG: GO TO 3.

    Fig 3: Checking APP Sensor Power Supply Circuit (2 Of 2)
    G02691895Courtesy of NISSAN MOTOR CO., U.S.A.
  3. CHECK APP SENSOR 2 POWER SUPPLY CIRCUIT-II 
    1. Turn ignition switch OFF.
    2. Disconnect ECM harness connector.
    3. Check harness continuity between APP sensor terminal 7 and ECM terminal 91. Refer to Wiring Diagram.

      Continuity should exist. 

    OK or NG

    OK: GO TO 4.

    NG: Repair open circuit.

  4. CHECK APP SENSOR 2 POWER SUPPLY CIRCUIT-II 

    Check the following.

    • Harness for short to power and short to ground, between the following terminals
    CHECKING HARNESS BETWEEN TERMINALS

    ECM terminal Sensor terminal
    47 Electric throttle control actuator terminal 2
    91 APP sensor terminal 7

    OK or NG

    OK: GO TO 5.

    NG: Repair short to ground or short to power in harness connectors.

  5. CHECK THROTTLE POSITION SENSOR 

    Refer to COMPONENT INSPECTION .

    OK or NG

    OK: GO TO  11.

    NG: GO TO 6.

  6. REPLACE ELECTRIC THROTTLE CONTROL ACTUATOR 
    1. Replace the electric throttle control actuator.
    2. Perform THROTTLE VALVE CLOSED POSITION LEARNING .
    3. Perform IDLE AIR VOLUME LEARNING .

      : INSPECTION END 

  7. CHECK APP SENSOR GROUND CIRCUIT FOR OPEN AND SHORT 
    1. Turn ignition switch OFF.
    2. Disconnect ECM harness connector.
    3. Check harness continuity between ECM terminal 82 and APP sensor terminal 1, ECM terminal 83 and APP sensor terminal 3.

      Refer to Wiring Diagram.

      Continuity should exist. 

    4. Also check harness for short to ground and short to power.

    OK or NG

    OK: GO TO 8.

    NG: Repair open circuit or short to ground or short to power in harness or connectors.

  8. CHECK APP SENSOR INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT 
    1. Check harness continuity between ECM terminal 106 and APP sensor terminal 2, ECM terminal 98 and APP sensor terminal 5.
    2. Refer to Wiring Diagram.

      Continuity should exist. 

    3. Also check harness for short to ground and short to power.

    OK or NG

    OK: GO TO 9.

    NG: Repair open circuit or short to ground or short to power in harness or connectors.

  9. CHECK ACCELERATOR PEDAL POSITION SENSOR 

    Refer to COMPONENT INSPECTION .

    OK or NG

    OK: GO TO  11.

    NG: GO TO 10.

  10. REPLACE ACCELERATOR PEDAL ASSEMBLY 
    1. Replace the accelerator pedal assembly.
    2. Perform ACCELERATOR PEDAL RELEASED POSITION LEARNING .
    3. Perform THROTTLE VALVE CLOSED POSITION LEARNING .
    4. Perform IDLE AIR VOLUME LEARNING .

      : INSPECTION END 

  11. CHECK INTERMITTENT INCIDENT 

    Refer to TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT .

    : INSPECTION END