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AUTOMATIC TRANSMISSION SYSTEM, Diagnostic DTC:U0100

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DTC Code DTC Name
U0100 Lost Communication with ECM / PCM "A"
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DESCRIPTION

The ECM communicates with the TCM via the Controller Area Network (CAN).

If there is a problem in communication, the TCM stores this DTC.

DTC No. Detection Item DTC Detection Condition Trouble Area MIL Memory
U0100 Lost Communication with ECM / PCM "A"

1. Diagnosis Condition 2. Malfunction Status 3. Malfunction Time 4. Other


  1. The engine switch is on (IG) and battery voltage is 10.5 V or more.

  2. There is no communication between the ECM and TCM.

  3. 1.25 seconds or more

  4. 1-trip detection logic

  • Harness and connector

  • ECM

  • TCM

 Comes on DTC stored
Table 1. *a from EFI-MAIN Relay *b CAN Communication Line
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WIRING DIAGRAM

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CAUTION / NOTICE / HINT

Note:

  • Inspect the fuses for circuits related to this system before performing the following procedure.

  • Perform registration and/or initialization when parts related to the automatic transmission are replaced.

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Tip:

  • If the CAN communication system malfunctions, the TCM cannot receive current data from the ECM. In this case, the freeze frame data output from the TCM is not updated, so the data will not be useful for the inspection. However, reading the Data List as the first step in troubleshooting is an effective way to find malfunctions.

  • The malfunctioning area can be checked using the CAN Bus Check function on the GTS.

Tip:

After the repair, clear the DTCs and perform the following procedure to check that DTCs are not output.


  1. Check the battery voltage is 10.5 V or more.

  2. Turn the engine switch on (IG).

  3. Check for DTCs again.

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PROCEDURE


  1. Click here

    CHECK TERMINAL VOLTAGE (POWER SOURCE OF ECM)


    1. B0065HNC17
      *a

      Rear view of wire harness connector

      (to ECM)

      Disconnect the A77 ECM 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 Condition Specified Condition
      A77-6 (+B2) - Body ground Engine switch on (IG) 11 to 14 V
      A77-7 (+B) - Body ground Engine switch on (IG) 11 to 14 V
      Result
      Proceed to
      OK
      NG

    • OKClick here
    • NG

      GO TO ECM POWER SOURCE CIRCUIT (ENGINE CONTROL SYSTEM / SFI SYSTEM) w/o Canister Pump Module:Click here

      GO TO ECM POWER SOURCE CIRCUIT (ENGINE CONTROL SYSTEM / SFI SYSTEM) w/ Canister Pump Module:Click here

  2. Click here

    CHECK HARNESS AND CONNECTOR (ECM - BODY GROUND)


    1. Disconnect the F4 ECM connector.

    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      F4-1 (E1) - Body ground Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    • OKClick here
    • NG

      REPAIR OR REPLACE HARNESS OR CONNECTOR (ECM - BODY GROUND)

  3. Click here

    CHECK HARNESS AND CONNECTOR (ECM - TCM)


    1. Disconnect the A78 ECM connector.

    2. Disconnect the A79 TCM connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A78-9 (CAN+) - A79-21 (CAN+) Always Below 1 Ω
      A78-10 (CAN-) - A79-13 (CAN-) Always Below 1 Ω
      A78-9 (CAN+) or A79-21 (CAN+) - Body ground Always 10 kΩ or higher
      A78-10 (CAN-) or A79-13 (CAN-) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    • OKClick here
    • NG

      REPAIR OR REPLACE HARNESS OR CONNECTOR

  4. Click here

    REPLACE TCM


    1. Replace the TCM.

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      Result
      Proceed to
      NEXT

  5. Click here

    CHECK DTC OUTPUT


    1. Clear the DTCs.


      1. Powertrain > ECT > Clear DTCs


    2. Start the engine.

    3. Read the DTCs.


      1. Powertrain > ECT > Trouble Codes


      Result
      Result Proceed to
      DTCs are not output A
      DTC U0100 is output B

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    REPLACE ECM


    1. Replace the ECM.

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      Result
      Proceed to
      NEXT