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Home >> Lexus >> 2024 >> RX 500h >> Repair and Diagnosis >> External Pages >> Different car >> Section 125 ( Automatic Transaxle System - Diagnostic Codes (3 Of 3) & Circuit Tests) >> Automatic Transaxle System >> DTC U0291-87: Lost Communication with Gear Shift Control Module "B" Missing Message [08/2023 - ] >> Procedure

DTC U0291-87: Lost Communication with Gear Shift Control Module "B" Missing Message [08/2023 - ]: Procedure

WARNING: This page is about a different car, the 2025 Lexus RX 350, 2024 Lexus RX 350, and 2023 Lexus RX 350. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK DTC OUTPUT (HEALTH CHECK) 

    Pre-procedure1

    • None
    • Enter the following menus: Health Check.
    • Check for DTCs.

      Result

      Result Proceed to
      Only U0291-87 is output. A
      DTCs other than U0291-87 are not output B

    Post-procedure1

    • Turn the engine switch off.

    Result: 

    B 

    GO TO DTC CHART. Refer to  DIAGNOSTIC TROUBLE CODE CHART [08/2023 - 10/2024]  , or refer to  DIAGNOSTIC TROUBLE CODE CHART [10/2024 - ] 

    Result: 

    A 

    See step  2

  2. CHECK VEHICLE CONDITION 
    1. Choose the model to be inspected.

      Result

      Result Proceed to
      w/o Advanced Park (Remote Controlled) A
      w/ Advanced Park (Remote Controlled) B

    Result: 

    B 

    See step  6

    Result: 

    A 

    See step  3

  3. CHECK SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU) (BAT1 TERMINAL VOLTAGE) 

    Pre-procedure1

    • Disconnect the B58 shift control actuator assembly connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition Result
      B58-8 (BAT1) - Body ground Ignition switch off 11 to 14 V V

      HINT: 

      As there might be an intermittent malfunction in the shift control actuator assembly (shift actuator ECU) power source circuit, inspect the following even if the measured voltage is as specified:

      • Installation condition of fuse(s) (before removing fuse(s)) (BAT1 circuit)
      • Fuse condition (before and after removing fuse(s)) (BAT1 circuit)
      • Connection condition of connectors (BAT1 circuit)
      • Wire harness condition (BAT1 circuit)
      • Wire harness condition (GND circuit)

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the B58 shift control actuator assembly connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (SHIFT ACTUATOR ECU POWER SOURCE CIRCUIT) 

    Result: 

    OK 

    See step  4

  4. CHECK SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU) (IGR1 TERMINAL VOLTAGE) 

    Pre-procedure1

    • Disconnect the B56 shift control actuator assembly connector.
    • Turn the ignition switch to ON.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition Result
      B56-5 (IGR1) - Body ground Ignition switch ON 11 to 14 V V

      HINT: 

      As there might be an intermittent malfunction in the shift control actuator assembly (shift actuator ECU) power source circuit, inspect the following even if the measured voltage is as specified:

      • Installation condition of fuse(s) (before removing fuse(s)) (IGR1 circuit)
      • Fuse condition (before and after removing fuse(s)) (IGR1 circuit)
      • Connection condition of connectors (IGR1 circuit)
      • Wire harness condition (IGR1 circuit)
      • Wire harness condition (GND circuit)

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Turn the ignition switch OFF.
    • Connect the B56 shift control actuator assembly connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (SHIFT ACTUATOR ECU POWER SOURCE CIRCUIT) 

    Result: 

    OK 

    See step  5

  5. CHECK HARNESS AND CONNECTOR (SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU) - ECM) 

    Pre-procedure1

    • Disconnect the B29 ECM connector.
      NOTE:
      • Before disconnecting the connector, check that it is not loose or disconnected.
      • Check that each connector between the ECM and shift control actuator assembly (shift actuator ECU) is not loose or disconnected.
    • Disconnect the B56 shift control actuator assembly connector.
      NOTE:
      • Before disconnecting the connector, check that it is not loose or disconnected.
      • Check the terminals of the connector for deformation and corrosion.
    • Disconnect the C35 transmission floor shift assembly connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Switch Condition Specified Condition Result
      B29-49 (CAN+) - B56-4 (CA3H) Ignition switch off Below 1 Ω Ω
      B29-48 (CAN-) - B56-3 (CA3L) Ignition switch off Below 1 Ω Ω
      B56-4 (CA3H) - Body ground and other terminals Ignition switch off 10 kΩ or higher kΩ
      B56-3 (CA3L) - Body ground and other terminals Ignition switch off 10 kΩ or higher kΩ
      NOTE:

      Make sure that each connector between the ECM and shift control actuator assembly (shift actuator ECU) is not loose or disconnected and its terminals are not deformed or corroded.

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the C35 transmission floor shift assembly connector.
    • Connect the B56 shift control actuator assembly connector.
    • Connect the B29 ECM connector.

    Result: 

    OK 

    REPLACE SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU). Refer to  REMOVAL [10/2022 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  6. CHECK SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU) (BAT1 TERMINAL VOLTAGE) 

    Pre-procedure1

    • Disconnect the B58 shift control actuator assembly connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition Result
      B58-8 (BAT1) - Body ground Ignition switch off 11 to 14 V V

      HINT: 

      As there might be an intermittent malfunction in the shift control actuator assembly (shift actuator ECU) power source circuit, inspect the following even if the measured voltage is as specified:

      • Installation condition of fuse(s) (before removing fuse(s)) (BAT1 circuit)
      • Fuse condition (before and after removing fuse(s)) (BAT1 circuit)
      • Connection condition of connectors (BAT1 circuit)
      • Wire harness condition (BAT1 circuit)
      • Wire harness condition (GND circuit)

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the B58 shift control actuator assembly connector.

    Result: 

    OK 

    See step  4

    Result: 

    NG 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (B1E1 TERMINAL VOLTAGE) 

    Pre-procedure1

    • Disconnect the H194 second power supply remote parking circuit connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      H194-1 (B1E1) - Body ground Always 11 to 14 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the H194 second power supply remote parking circuit connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  8

  8. CHECK HARNESS AND CONNECTOR (SECOND POWER SUPPLY REMOTE PARKING CIRCUIT - SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU)) 

    Pre-procedure1

    • Disconnect the H194 second power supply remote parking circuit connector.
    • Disconnect the B58 shift control actuator assembly (shift actuator ECU) connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      H194-8 (BOE) - B58-8 (BAT1) Always Below 1 Ω Ω
      H194-8 (BOE) or B58-8 (BAT1) - Body ground and other terminals Always 10 kΩ or higher kΩ

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the H194 second power supply remote parking circuit connector.
    • Connect the B58 shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    OK 

    REPLACE SECOND POWER SUPPLY REMOTE PARKING CIRCUIT. Refer to  REMOVAL [08/2023 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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