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DTC U0101: Lost Communication with TCM [11/2021 - ]: Procedure

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  1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC U0101) 
    1. Connect the Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Turn the Techstream on.
    4. Enter the following menus: System Select / Health Check.
    5. Read the DTCs.

      Result

      Result Proceed to
      DTC U0101 is output A
      DTC U0101 and other DTCs are output B

      HINT: 

      If any DTCs other than U0101 are output, troubleshoot those DTCs first.

    Result: 

    B 

    GO TO DTC CHART. Refer To  DIAGNOSTIC TROUBLE CODE CHART [11/2021 - ] 

    Result: 

    A 

    See step  2

  2. CHECK TERMINAL VOLTAGE (POWER SOURCE OF TCM) 
    GTY1082724Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *a Front view of wire harness connector
    (to TCM)
    1. Disconnect the TCM connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A118-6 (BATT) - A118-2 (E1) Always 11 to 14 V
    3. Turn the engine switch on (IG).
    4. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A118-5 (+B) - A118-2 (E1) Engine switch on (IG) 11 to 14 V
      A118-16 (IG2) - A118-2 (E1) Engine switch on (IG) 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    GO TO TCM POWER SOURCE CIRCUIT. Refer to  TCM Power Source Circuit [11/2021 - ] 

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (TCM - ECM) 
    1. Disconnect the TCM connector.
    2. Disconnect the ECM connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A118-21 (CAN+) - A117-9 (CAN+) Always Below 1 Ω
      A118-13 (CAN-) - A117-10 (CAN-) Always Below 1 Ω
      A118-21 (CAN+) or A117-9 (CAN+) - Body ground Always 10 kΩ or higher
      A118-13 (CAN-) or A117-10 (CAN-) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

  4. REPLACE TCM 
    1. Replace the TCM.

      Refer to REMOVAL [11/2021 - ]

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  5

  5. CHECK WHETHER DTC OUTPUT RECURS (DTC U0101) 
    1. Connect the Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Turn the Techstream on.
    4. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [11/2021 - ]

      Powertrain > Engine > Clear DTCs 

    5. Turn the engine switch off and wait for at least 30 seconds.
    6. Turn the engine switch on (IG) and turn the Techstream on.
    7. Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
    8. Enter the following menus: Powertrain / Engine / Trouble Codes.
    9. Read the DTCs.

      Powertrain > Engine > Trouble Codes 

      Result

      Result Proceed to
      DTCs are is not output A
      DTC U0101 is output B

    Result: 

    A 

    END 

    Result: 

    B 

    REPLACE ECM. Refer to  REMOVAL [11/2021 - ] 

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