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Home › Lexus › 2005 › RX 330 AWD › Repair and Diagnosis › External Pages › Different car › Section 573 (Multiplex Communication) › Multiplex Communication System › DTC B1271: Combination Meter ECU Communication Stop › Inspection Procedure

Inspection Procedure

WARNING: This page is about a different car, the 2008 Lexus RX 350. However, it is still accessible from the selected car via links, so may be relevant.

HINT:

When "+B or GND short malfunction of communication bus" DTCs (B1266 and B1267) are detected at the same time as "communication stop" DTC B1271, repair the "+B or GND short malfunction of communication bus" DTCs first.

  1. INSPECT FUSE (DOME, ECU-B) 
    1. Remove the DOME and ECU-B fuses from the fusible link block.
    2. Measure the resistance of the fuses.

      Standard resistance: 

      Below 1 Ω 

    NG: REPLACE FUSE 

    OK: Go to Next Step 

  2. CHECK WIRE HARNESS (COMBINATION METER ECU - BATTERY AND BODY GROUND) 
      Fig 1: Identifying C8 & C9 Connector Terminals
      G05275010Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Disconnect the C8 and C9 ECU connectors.
    2. Measure the voltage and resistance of the wire harness side connector.

      Standard voltage 

      VOLTAGE SPECIFICATION TABLE

      Tester Connection Condition Specified Condition
      C8-15 - Body ground Always 10 to 14 V
      C8-16 - Body ground Always 10 to 14 V

      Standard resistance 

      RESISTANCE SPECIFICATION TABLE

      Tester Connection Specified Condition
      C8-1 - Body ground Below 1 Ω
      C9-1 - Body ground Below 1 Ω

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to Next Step 

  3. CHECK RESISTANCE OF COMMUNICATION LINE 
      Fig 2: Identifying C8, C9, A20, G3 & C4 ECU Connector Terminals
      G05275011Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Disconnect the C8, C9, A20, G3 and C4 ECU connectors.
    2. Measure the resistance between the specified terminals on the wire harness side connectors.

      Standard resistance 

      RESISTANCE SPECIFICATION TABLE

      Tester Connection Specified Condition
      C9-4 - MPX1 (A20-24) Below 1 Ω
      C8-5 - MPI2 (G3-13) (*1) Below 1 Ω
      C8-5 - MPX+ (C4-5) (*2) Below 1 Ω
      HINT:
      *1: with LEXUS Navigation System
      *2: without LEXUS Navigation System

      Result 

      RESULT TABLE

      Result Proceed to
      Both are OK A
      One is OK B
      Both are NG C

    B: REPLACE COMBINATION METER ECU AND REPAIR OR REPLACE HARNESS OR CONNECTOR 

    C: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: REPLACE COMBINATION METER ECU 

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