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Home >> Lexus >> 2007 >> GS 450h >> Repair and Diagnosis >> Accessories & Equipment >> Communication Devices >> Multiplex Communication >> Multiplex Communication System >> DTC B1296 Front Light ECU Communication Stop >> Inspection Procedure

Inspection Procedure

  1. CHECK OPERATION 
    1. Turn the headlight dimmer switch ON and check that the headlights illuminate.

      OK: 

      Headlights illuminate. 

    OK: REPLACE ENGINE ROOM NO. 1 RELAY BLOCK, JUNCTION BLOCK (FRONT CONTROLLER) 

    NG: GO TO Next Step 

  2. INSPECT FUSE (MPX-B) 
    1. Remove the MPX-B fuse from the engine room No. 1 relay block, junction block.
    2. Measure the resistance of the fuses.

      Standard resistance: 

      Below 1 Ω 

    NG: REPLACE FUSE 

    OK: GO TO Next Step 

  3. CHECK WIRE HARNESS (FRONT CONTROLLER - BATTERY AND BODY GROUND) 
    Fig 1: Identifying 1X And 1Y Engine Room No. 1 Junction Block Connector Terminals
    G05312296Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Disconnect the 1X and 1Y engine room No. 1 junction block connectors.
    2. Measure the voltage and resistance of the wire harness side connectors.

      Standard voltage 

      TESTER CONNECTION SPECIFIED CONDITION

      Tester Connection Specified Condition
      1X-4 - Body ground 10 to 14 V

      Standard resistance 

      TESTER CONNECTION SPECIFIED CONDITION

      Tester Connection Specified Condition
      1Y - 1 - Body ground Below 1 Ω

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: GO TO Next Step 

  4. CHECK RESISTANCE OF COMMUNICATION LINE 
    Fig 2: Identifying K22 Combination Switch (Windshield Wiper Switch) Connector Terminals
    G05312297Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Disconnect the K22 switch connector.
    2. Disconnect the A29 ECU connector.
    3. Disconnect the 1X engine room No. 1 junction block connector.
    4. Measure the resistance of the wire harness side connectors.

      Standard resistance 

      TESTER CONNECTION SPECIFIED CONDITION

      Tester Connection Specified Condition
      1X-5 - K22-7 (MPX2) Below 1 Ω
      1X-6-A29-6 (MPX1) Below 1 Ω

      Result 

      RESULT REFERENCE CHART

      Result Proceed to
      All are OK A
      One or two is / are OK B
      All are NG C

    B: REPAIR OR REPLACE ENGINE ROOM NO. 1 RELAY BLOCK, JUNCTION BLOCK AND WIRE HARNESS OR CONNECTOR 

    C: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    A: GO TO Next Step 

  5. CHECK OPERATION OF FRONT CONTROLLER 
    1. After replacing the front controller with a normally functioning controller, check that the headlights illuminate.

      OK: 

      Headlights illuminate. 

    NG: REPLACE ENGINE ROOM NO. 1 RELAY BLOCK, JUNCTION BLOCK 

    OK: REPLACE FRONT CONTROLLER 

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