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Home >> Lexus >> 2024 >> RX 500h >> Repair and Diagnosis >> External Pages >> Different car >> Section 12 (Electronic A/T Shift Lever System - Diagnostic Codes (2 Of 2) & Circuit Tests) >> Electronic Shift Lever System >> DTC U0291-00: Lost Communication with Gear Shift Control Module "B" (System 2) Missing Message [10/2022 - ] >> Procedure

DTC U0291-00: Lost Communication with Gear Shift Control Module "B" (System 2) Missing Message [10/2022 - ]: 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 (TRANSMISSION) 

    Pre-procedure1

    • Turn the ignition switch to ON.
    • Check for DTCs.

      Powertrain > Transmission > Trouble Codes 

      Result

      Result Proceed to
      P1779-96 is output A
      P1779-96 is not output B

    Post-procedure1

    • Turn the ignition switch off.

    Result: 

    A 

    GO TO DTC CHART (P1779-96). Refer to  DTC P1779-96: Gear Shift Control Module Backup Power Supply Component Internal Failure [10/2022 - 08/2023]  , or refer to  DTC P1779-96: Gear Shift Control Module Backup Power Supply Component Internal Failure [08/2023 - ] 

    Result: 

    B 

    See step  2

  2. CHECK DTC OUTPUT (HEALTH CHECK) 

    Pre-procedure1

    • Turn the ignition switch to ON.
    • Using the GTS, perform a Health Check.

      Result

      Result Proceed to
      Only U0291-00 is output A
      U0291-00 and other DTCs are output B

    Post-procedure1

    • Turn the ignition switch off.

    Result: 

    B 

    GO TO DTC CHART 

    Result: 

    A 

    See step  3

  3. CHECK FOR SHORT TO GND IN CAN BUS LINE (ECU CONNECTED) 

    Pre-procedure1

    • Disconnect the cable from the negative (-) battery terminal.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      C35-21 (CA3H) or C35-6 (CA3L) - Body ground Cable disconnected from negative (-) battery terminal 200 Ω or higher Ω
      GTY1128056Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Transmission Floor Shift Assembly (Shift Control ECU))

      Result

      Result
      OK
      NG

    Post-procedure1

    • Connect the cable to the negative (-) battery terminal.

    Result: 

    NG 

    See step  7

    Result: 

    OK 

    See step  4

  4. CHECK FOR OPEN IN CAN BUS LINE (ECU CONNECTED) 

    Pre-procedure1

    • Disconnect the cable from the negative (-) battery terminal.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      C35-21 (CA3H) - C35-6 (CA3L) Cable disconnected from negative (-) battery terminal 54 to 69 Ω Ω
      GTY1129523Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Transmission Floor Shift Assembly (Shift Control ECU))

      Result

      Result
      OK
      NG

    Post-procedure1

    • Connect the cable to the negative (-) battery terminal.

    Result: 

    OK 

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

    Result: 

    NG 

    See step  5

  5. CHECK FOR OPEN IN CAN BUS LINE (ECM DISCONNECTED) 

    Pre-procedure1

    • Disconnect the cable from the negative (-) battery terminal.
    • Disconnect the B29 ECM connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      C35-21 (CA3H) - C35-6 (CA3L) Cable disconnected from negative (-) battery terminal 108 to 132 Ω Ω

      Result

      Result
      OK
      NG

    Post-procedure1

    • Connect the ECM connector.
    • Connect the cable to the negative (-) battery terminal.

    Result: 

    OK 

    REPLACE ECM. Refer to  REMOVAL [10/2022 - ] 

    Result: 

    NG 

    See step  6

  6. CHECK FOR OPEN IN CAN MAIN BUS LINE (SHIFT CONTROL ECU DISCONNECTED) 

    Pre-procedure1

    • Disconnect the cable from the negative (-) battery terminal.
    • Disconnect the C35 transmission floor shift assembly (shift control ECU) connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      C35-21 (CA3H) - C35-6 (CA3L) Cable disconnected from negative (-) battery terminal 108 to 132 Ω Ω

      Result

      Result
      OK
      NG

    Post-procedure1

    • Connect the transmission floor shift assembly (shift control ECU) connector.
    • Connect the cable to the negative (-) battery terminal.

    Result: 

    OK 

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

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  7. CHECK FOR SHORT TO GND IN CAN BUS LINE (SHIFT CONTROL ECU DISCONNECTED) 

    Pre-procedure1

    • Disconnect the cable from the negative (-) battery terminal.
    • Disconnect the C35 transmission floor shift assembly (shift control ECU) connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      C35-21 (CA3H) or C35-6 (CA3L) - Body ground Cable disconnected from negative (-) battery terminal 200 Ω or higher Ω

      Result

      Result
      OK
      NG

    Post-procedure1

    • Connect the transmission floor shift assembly (shift control ECU) connector.
    • Connect the cable to the negative (-) battery terminal.

    Result: 

    OK 

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

    Result: 

    NG 

    See step  8

  8. CHECK FOR SHORT TO GND IN CAN BUS LINE (ECM DISCONNECTED) 

    Pre-procedure1

    • Disconnect the cable from the negative (-) battery terminal.
    • Disconnect the B29 ECM connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      C35-21 (CA3H) or C35-6 (CA3L) - Body ground Cable disconnected from negative (-) battery terminal 200 Ω or higher Ω

      Result

      Result
      OK
      NG

    Post-procedure1

    • Connect the ECM connector.
    • Connect the cable to the negative (-) battery terminal.

    Result: 

    OK 

    REPLACE ECM. Refer to  REMOVAL [10/2022 - ] 

    Result: 

    NG 

    See step  9

  9. CHECK FOR SHORT TO GND IN CAN BUS LINE (SHIFT ACTUATOR ECU DISCONNECTED) 

    Pre-procedure1

    • Disconnect the cable from the negative (-) battery terminal.
    • Disconnect the B56 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
      C35-21 (CA3H) or C35-6 (CA3L) - Body ground Cable disconnected from negative (-) battery terminal 200 Ω or higher Ω

      Result

      Result
      OK
      NG

    Post-procedure1

    • Connect the shift control actuator assembly (shift actuator ECU) connector.
    • Connect the cable to the negative (-) battery terminal.

    Result: 

    OK 

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

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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