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Home >> Infiniti >> 2008 >> QX56 AWD >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Engine Control System - DTCS P1148 To P2A03 >> DTC P1805: Brake Switch >> Diagnosis Procedure
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Diagnosis Procedure

  1. CHECK STOP LAMP SWITCH CIRCUIT
    1. Turn ignition switch OFF.
    2. Check the stop lamp when depressing and releasing the brake pedal.
      BRAKE PEDAL REFERENCE CHART

      Brake pedal Stop lamp
      Fully released Not illuminated
      Slightly depressed Illuminated

    OK or NG 

    OK: GO TO  4.

    NG: GO TO 2.

  2. CHECK STOP LAMP SWITCH POWER SUPPLY CIRCUIT
    1. Disconnect stop lamp switch harness connector.
      Fig 1: Checking ASCD Brake Switch Power Supply Circuit
      G05739659Courtesy of NISSAN MOTOR CO., U.S.A.
    2. Check voltage between stop lamp switch terminal 3 and ground with CONSULT-III or tester.

      Voltage: Battery voltage 

    OK or NG 

    OK: GO TO  4.

    NG: GO TO 3.

    Fig 2: Checking Voltage Between Stop Lamp Switch Terminal 1 And Ground
    G05739660Courtesy of NISSAN MOTOR CO., U.S.A.
  3. DETECT MALFUNCTIONING PART

    Check the following.

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

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

  4. CHECK STOP LAMP 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 101 and stop lamp switch terminal 4.

      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 5.

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

  5. CHECK STOP LAMP SWITCH

    Refer to "COMPONENT INSPECTION ".

    OK or NG 

    OK: GO TO 6.

    NG: Replace stop lamp switch.

  6. CHECK INTERMITTENT INCIDENT

    Refer to "HOW TO CHECK TERMINAL " and "INTERMITTENT INCIDENT ".

    INSPECTION END