Mike's Workshop Manuals: Service manuals for every vehicle
Home >> Infiniti >> 2009 >> QX56 AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - DTCS P1140 To P2A03 >> DTC P1805: Brake Switch >> Diagnosis Procedure

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.
      STOP LAMP ILLUMINATION CONDITION

      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: Identifying ASCD Brake And Stop Lamp Switch
      G06315782Courtesy 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 3 And Ground
      G06315783Courtesy 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