SFI SYSTEM, Diagnostic DTC:U0101

DTC Code DTC Name
U0101 Lost Communication with TCM

MONITOR DESCRIPTION

The Transmission Control Module (TCM) and ECM perform 2-way communication with each other via the Controller Area Network (CAN). The TCM sends signals to the ECM concerning required engine speed, required engine torque, warning indicators in the combination meter assembly, DTCs and other data. The ECM sends signals to the TCM concerning engine speed, opening angle of the throttle valve, temperature of intake air, temperature of engine coolant, engine torque and other data. If the TCM cannot communicate with the ECM, the TCM will conclude that there is a malfunction in the CAN system, illuminate the MIL and store a DTC.

DTC No. DTC Detection Condition Trouble Area
U0101

  • All of the following conditions are met for 1.25 seconds (1 trip detection logic):


    1. Engine switch on (IG)

    2. Battery voltage 10.5 V or higher

    3. No communication between ECM and TCM

  • ECM to TCM circuit

  • TCM

  • ECM

MONITOR STRATEGY

Related DTCs U0101: Lost communication with TCM
Required Sensors/Components (Main) ECM
Required Sensors/Components (Related) -
Frequency of Operation Continuous
Duration 1.25 seconds
MIL Operation Immediate
Sequence of Operation None

TYPICAL ENABLING CONDITIONS

Monitor runs whenever the following DTCs are not stored None
Battery voltage 10.5 V or higher (More than 1 second)
Engine switch On (IG)
Starter Off

TYPICAL MALFUNCTION THRESHOLDS

Communication signal Lost communication with TCM

CONFIRMATION DRIVING PATTERN


  1. Connect the Techstream to the DLC3.

  2. Turn the engine switch on (IG) and turn the Techstream on.

  3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).

  4. Turn the engine switch off and wait for at least 30 seconds.

  5. Turn the engine switch on (IG) and turn the Techstream on.

  6. Wait 5 seconds or more.

  7. Enter the following menus: Powertrain / Engine / Trouble Codes.

  8. Read the pending DTCs.

    Tech Tips


    • If a pending DTC is output, the system is malfunctioning.

    • If a pending DTC is not output, perform the following procedure.

  9. Enter the following menus: Powertrain / Engine / Utility / All Readiness.

  10. Input the DTC: U0101.

  11. Check the DTC judgment result.

    Techstream Display Description
    NORMAL

    • DTC judgment completed

    • System normal
    ABNORMAL

    • DTC judgment completed

    • System abnormal
    INCOMPLETE

    • DTC judgment not completed

    • Perform driving pattern after confirming DTC enabling conditions
    N/A

    • Unable to perform DTC judgment

    • Number of DTCs which do not fulfill DTC preconditions has reached ECU's memory limit

    Tech Tips


    • If the judgment result shows NORMAL, the system is normal.

    • If the judgment result shows ABNORMAL, the system has a malfunction.

  12. If the judgment result is INCOMPLETE or N/A and no pending DTC is output, perform a universal trip and check for permanent DTCs Click here.

    Tech Tips


    • If a permanent DTC is output, the system is malfunctioning.

    • If no permanent DTC is output, the system is normal.

WIRING DIAGRAM

A01HPM7E20

INSPECTION PROCEDURE

Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE


  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

      Tech Tips

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


    B

    GO TO DTC CHART

    A

  2. CHECK TERMINAL VOLTAGE (POWER SOURCE OF TCM)


    1. A01HQCQE11
      Text in Illustration
      *a

      Front view of wire harness connector

      (to TCM)

      Disconnect the TCM connector.

    2. Turn the engine switch on (IG).

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      E7-1 (BATT) - E7-8 (E1) Always 11 to 14 V
      E7-18 (+B) - E7-8 (E1) Engine switch on (IG) 11 to 14 V

    NG

    GO TO TCM POWER SOURCE CIRCUIT Click here

    OK

  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
      E7-6 (CAN+) - E26-31 (CAN+) Always Below 1 Ω
      E7-7 (CAN-) - E26-1 (CAN-) Always Below 1 Ω
      E7-6 (CAN+) or E26-31 (CAN+) - Body ground Always 10 kΩ or higher
      E7-7 (CAN-) or E26-1 (CAN-) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. REPLACE TCM


    1. Replace the TCM Click here.


    NEXT

  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 Click here.

    5. Turn the engine switch off.

    6. Turn the engine switch on (IG).

    7. Turn the Techstream on.

    8. Wait for 5 seconds or more.

    9. Enter the following menus: Powertrain / Engine / Trouble Codes.

    10. Read the DTCs.

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

    B

    REPLACE ECM Click here

    A

    END