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Home >> Lexus >> 2021 >> LC 500 2D Coupe >> Repair and Diagnosis >> Accessories & Equipment >> Communication Devices >> Can Communication System - Circuit Tests (Coupe) (1 Of 6) & Diagnostic Codes >> Can Communication System >> Main Body ECU Communication Stop Mode [05/2023 - ] >> Procedure

Main Body ECU Communication Stop Mode [05/2023 - ]: Procedure

  1. CHECK FOR OPEN IN CAN BUS WIRE (MAIN BODY ECU [MULTIPLEX NETWORK BODY ECU] BRANCH WIRE) 
    1. Disconnect the cable from the negative (-) battery terminal.
    2. Disconnect the main body ECU (multiplex network body ECU) connector.
      GTY784495Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Main Body ECU [Multiplex Network Body ECU])
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      P7-5 (CANH) - P7-4 (CANL) Cable disconnected from negative (-) battery terminal 54 to 69 Ω

      Result

      Result 
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE CAN BRANCH WIRE OR CONNECTOR 

    Result: 

    OK 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT) 
    1. Remove the main body ECU (multiplex network body ECU).

      Refer to REMOVAL [05/2023 - ]

    2. Reconnect the junction block assembly LH connectors.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A-11 (GND1) - Body ground Cable disconnected from negative (-) battery terminal Below 1 Ω
      GTY766896Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component without harness connected
      (Main Body ECU [Multiplex Network Body ECU])
    4. Reconnect the cable to the negative (-) battery terminal.
      NOTE:

      When disconnecting the cable, some systems need to be initialized after the cable is reconnected.

      Refer to WORK PROCEDURE [05/2023 - ]

    5. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A-31 (BECU) - Body ground Always 11 to 14 V
      A-30 (ACC) - Body ground Engine switch on (ACC) 11 to 14 V
      Engine switch off Below 1 V
      A-32 (IG) - Body ground Engine switch on (IG) 11 to 14 V
      Engine switch off Below 1 V

      Result

      Result 
      OK
      NG

    Result: 

    OK 

    REPLACE MAIN BODY ECU (MAIN BODY ECU [MULTIPLEX NETWORK BODY ECU]). Refer to  REMOVAL [05/2023 - ] 

    Result: 

    NG 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT) 
    1. Disconnect the junction block assembly LH connectors.
      GTY785988Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Junction Block Assembly LH)      		 - -
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      3B-6 - Body ground Cable disconnected from negative (-) battery terminal Below 1 Ω
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      3F-1 - Body ground Always 11 to 14 V
      3E-1 - Body ground Always 11 to 14 V

      Result

      Result 
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

  4. CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT) 
    1. Measure the voltage according to the value(s) in the table below.
      GTY828588Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Junction Block Assembly LH)

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      3B-17 - Body ground Engine switch on (ACC) 11 to 14 V
      Engine switch off Below 1 V
      3B-18 - Body ground Engine switch on (IG) 11 to 14 V
      Engine switch off Below 1 V

      Result

      Result 
      OK
      NG

    Result: 

    OK 

    REPLACE JUNCTION BLOCK ASSEMBLY LH. Refer to  REMOVAL [05/2023 - ] 

    Result: 

    NG 

    GO TO SMART ACCESS SYSTEM WITH PUSH-BUTTON START. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [05/2023 - ] 

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