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Home >> Infiniti >> 2004 >> QX56 RWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System >> DTC P1572: ASCD Brake Switch >> Diagnostic Procedure
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Diagnostic Procedure

  1. CHECK OVERALL FUNCTION-I 

    Without CONSULT-II 

    1. Turn ignition switch ON.
    2. Select "BRAKE SW1" in "DATA MONITOR" mode with CONSULT-II.
    3. Check "BRAKE SW1" indication under the following conditions.
    BRAKE CHECKING CONDITION

    CONDITION INDICATION
    When brake pedal is depressed OFF
    When brake pedal is fully released ON
    Fig 1: Select "BRAKE SW1" In "DATA MONITOR" Mode With CONSULT-II
    G02691826Courtesy of NISSAN MOTOR CO., U.S.A.

    Without CONSULT-II 

    1. Turn ignition switch ON.
    2. Check voltage between ECM terminal 108 and ground under the following conditions.
    CHECKING VOLTAGE CONDITION

    CONDITION VOLTAGE
    When brake pedal is depressed Approximately 0V
    When brake pedal is fully released Battery voltage
    Fig 2: Checking Voltage Between ECM Terminal 108 & Ground
    G02691827Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG

    OK: GO TO 2.

    NG: GO TO  3.

  2. CHECK OVERALL FUNCTION-II 

    With CONSULT-II 

    Check "BRAKE SW2" indication in "DATA MONITOR" mode.

    BRAKE CHECKING CONDITION

    CONDITION INDICATION
    When brake pedal is released OFF
    When brake pedal is depressed ON
    Fig 3: Checking "BRAKE SW2" Indication In "DATA MONITOR" Mode.
    G02691828Courtesy of NISSAN MOTOR CO., U.S.A.

    Without CONSULT-II 

    Check voltage between ECM terminal 101 and ground under the following conditions.

    CHECKING VOLTAGE CONDITION

    CONDITION VOLTAGE
    When brake pedal is released Approximately 0V
    When brake pedal is depressed Battery voltage
    Fig 4: Checking Voltage Between ECM Terminal 101 & Ground
    G02691829Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG

    OK: GO TO  12.

    NG: GO TO  8.

  3. CHECK ASCD BRAKE SWITCH POWER SUPPLY CIRCUIT 
    1. Turn ignition switch OFF.
    2. Disconnect ASCD brake switch harness connector.
    3. Turn ignition switch ON.
      Fig 5: Identifying ASCD Brake Switch, Stop Lamp Switch & Brake Pedal
      G02691830Courtesy of NISSAN MOTOR CO., U.S.A.
  4. Check voltage between ASCD brake switch terminal 1 and ground with CONSULT-II or tester.

    Voltage: Battery voltage 

    OK or NG

    OK: GO TO  6.

    NG: GO TO 4.

    Fig 6: Checking Voltage Between ASCD Brake Switch Terminal 1 & Ground
    G02691831Courtesy of NISSAN MOTOR CO., U.S.A.
  5. DETECT MALFUNCTIONING PART 

    Check the following.

    • Harness connectors M31, E152
    • Fuse block (J/B) connector M4
    • 10A fuse
    • Harness for open or short between ASCD brake switch and fuse

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

  6. CHECK ASCD BRAKE SWITCH INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT 
    1. Turn ignition switch OFF.
    2. Disconnect ECM harness connector.
    3. Check harness continuity between ECM terminal 108 and ASCD brake switch terminal 2. Refer to Wiring Diagram.

      Continuity should exist. 

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

      OK or NG

      OK: GO TO 6.

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

  7. CHECK ASCD BRAKE SWITCH 

    Refer to COMPONENT INSPECTION .

    OK or NG

    OK: GO TO  12.

    NG: Replace ASCD brake switch.

  8. CHECK STOP LAMP SWITCH POWER SUPPLY CIRCUIT 
    1. Turn ignition switch OFF.
    2. Disconnect stop lamp switch harness connector.
      Fig 7: Identifying ASCD Brake Switch, Stop Lamp Switch & Brake Pedal
      G02691832Courtesy of NISSAN MOTOR CO., U.S.A.
    3. Check voltage between stop lamp switch terminal 1 and ground with CONSULT-II or tester.

      Voltage: Battery voltage 

      OK or NG

      OK: GO TO  10.

      NG: GO TO 8.

      Fig 8: Checking Voltage Between Stop Lamp Switch Terminal 1 & Ground
      G02691833Courtesy of NISSAN MOTOR CO., U.S.A.
  9. DETECT MALFUNCTIONING PART 

    Check the following.

    • Harness connectors M31, E152
    • Fuse block (J/B) connector M60
    • 10A fuse
    • Harness for open or short between stop lamp switch and fuse

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

  10. CHECK STOP LAMP SWITCH INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT 
    1. Disconnect ECM harness connector.
    2. Check harness continuity between ECM terminal 101 and stop lamp switch terminal 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 10.

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

  11. CHECK STOP LAMP SWITCH 

    Refer to COMPONENT INSPECTION .

    OK or NG

    OK: GO TO 11.

    NG: Replace stop lamp switch.

  12. CHECK INTERMITTENT INCIDENT 

    Refer to TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT .

    : INSPECTION END 

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