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Home >> Lexus >> 2024 >> RX 500h >> Repair and Diagnosis >> External Pages >> Different car >> Section 78 (Electronic A/T Shift Lever System - Diagnostic Codes & Circuit Tests) >> Electronic Shift Lever System >> DTC P1779-49: Gear Shift Control Module Backup Power Supply Internal Electronic Failure [10/2022 - ] >> Procedure

DTC P1779-49: Gear Shift Control Module Backup Power Supply Internal Electronic Failure [10/2022 - ]: Procedure

WARNING: This page is about a different car, the 2025 Lexus RX 450h+, 2025 Lexus RX 350h, 2024 Lexus RX 450h+, 2024 Lexus RX 350h, and 2023 Lexus RX 350h. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK HARNESS AND CONNECTOR (INTEGRATED CAPACITOR - SHIFT ACTUATOR ECU) 

    Pre-procedure1

    • Disconnect the H116 integration control supply (integrated capacitor) connector.
    • Disconnect the B56 shift control actuator assembly (shift actuator ECU) connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      H116-9 (BUAE) - Body ground Always Below 1 V V
      H116-19 (BUA) - Body ground Always Below 1 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the shift control actuator assembly (shift actuator ECU) connector.
    • Connect the integration control supply (integrated capacitor) connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (INTEGRATED CAPACITOR - SHIFT CONTROL ECU) 

    Pre-procedure1

    • Disconnect the H116 integration control supply (integrated capacitor) connector.
    • Disconnect the C35 transmission floor shift assembly (shift control ECU) connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      H116-1 (BUSE) - Body ground Always Below 1 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the transmission floor shift assembly (shift control ECU) connector.
    • Connect the integration control supply (integrated capacitor) connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (INTEGRATED CAPACITOR - POWER DISTRIBUTION BOX ASSEMBLY) 

    Pre-procedure1

    • Disconnect the H116 integration control supply (integrated capacitor) connector.
    • Disconnect the C90 power distribution box assembly connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      H116-10 (BUE2) - Body ground Always Below 1 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the power distribution box assembly connector.
    • Connect the integration control supply (integrated capacitor) connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

  4. INSPECT POWER DISTRIBUTION BOX ASSEMBLY 

    Pre-procedure1

    • Measure the resistance according to the value(s) in the table below.
      GTY1124651Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component without harness connected
      (Power Distribution Box Assembly)      		 - -

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      C90-27 or z31-25 (SBAT) - Other terminals Always 10 kΩ or higher kΩ

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Install the main body ECU (multiplex network body ECU) to the power distribution box assembly.

    Result: 

    NG 

    REPLACE POWER DISTRIBUTION BOX ASSEMBLY. Refer to  REMOVAL [10/2022 - 08/2023]  , or refer to  REMOVAL [08/2023 - ] 

    Result: 

    OK 

    See step  5

  5. CHECK HARNESS AND CONNECTOR (INTEGRATED CAPACITOR - BRAKE CONTROL POWER SUPPLY ASSEMBLY) 

    Pre-procedure1

    • Disconnect the H116 integration control supply (integrated capacitor) connector.
    • Disconnect the H159 brake control power supply assembly connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      H116-6 (BUA3) - Body ground Always Below 1 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the brake control power supply assembly connector.
    • Connect the integration control supply (integrated capacitor) connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  6

  6. CHECK BRAKE CONTROL POWER SUPPLY ASSEMBLY 

    Pre-procedure1

    • Disconnect the H116 integration control supply (integrated capacitor) connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      H116-6 (BUA3) - Body ground Always Below 1 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the integration control supply (integrated capacitor) connector.

    Result: 

    NG 

    REPLACE BRAKE CONTROL POWER SUPPLY ASSEMBLY. Refer to  REMOVAL [10/2022 - ] 

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (INTEGRATED CAPACITOR - DOOR LOCK ASSEMBLY) 

    Pre-procedure1

    • Disconnect the H116 integration control supply (integrated capacitor) connector.
    • Disconnect the D34 front door lock with motor assembly LH connector.
    • Disconnect the D15 front door lock with motor assembly RH connector.
    • Disconnect the E16 rear door lock with motor assembly LH connector.
    • Disconnect the E6 rear door lock with motor assembly RH connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      H116-20 (BUA2) - Body ground Always Below 1 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the rear door lock with motor assembly RH connector.
    • Connect the rear door lock with motor assembly LH connector.
    • Connect the front door lock with motor assembly RH connector.
    • Connect the front door lock with motor assembly LH connector.
    • Connect the integration control supply (integrated capacitor) connector.

    Result: 

    OK 

    REPLACE INTEGRATION CONTROL SUPPLY (INTEGRATED CAPACITOR). Refer to  REMOVAL [10/2022 - 08/2023]  , or refer to  REMOVAL [08/2023 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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