ECD SYSTEM, Diagnostic DTC:U0001/A2

DTC Code DTC Name
U0001/A2 High Speed CAN Communication Bus

DESCRIPTION

The Transmission Control Module (TCM) and ECM perform 2-way communications with each other via the Controller Area Network (CAN). The TCM sends signals to the ECM concerning required engine rpm, required engine torques, warning indicators in the combination meter, DTCs and other data. The ECM sends signals to the TCM concerning engine rpm, opening angles of the throttle valve, temperature of intake air, temperature of engine coolant, engine torques 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 set a DTC.

DTC No. DTC Detection Condition Trouble Area
U0001/A2 No communication from TCM continues

  • Open or short in TCM and ECM circuit

  • TCM

  • ECM

WIRING DIAGRAM

A01BA90E01

INSPECTION PROCEDURE

Note

After replacing the ECM, the new ECM needs registration Click here and initialization Click here.

Tech Tips

Read freeze frame data using the intelligent tester. 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 running or stopped, if the engine was warmed up or not, and other data from the time the malfunction occurred.

PROCEDURE


  1. CHECK ECM (VC, +B AND E1 TERMINALS)


    1. A01BF68E10

      Measure the voltage and resistance of the ECM connectors.

      Standard
      Tester Connection Ignition Switch Condition Specified Condition
      B9-1 (+B) - Body ground ON 9 to 14 V
      D1-18 (VC) - Body ground ON 4.5 to 5.5 V
      D3-7 (E1) - Body ground - 10 kΩ or higher

    NG

    CHECK ECM POWER SOURCE CIRCUIT

    OK

  2. CHECK TRANSMISSION CONTROL MODULE (IG2 AND E1 TERMINALS)


    1. A01BFV5E01

      Measure the voltage and resistance of the TCM connectors.

      Standard voltage
      Tester Connection Ignition switch Condition Specified Condition
      O3-6 (IG2) - Body ground Ignition switch ON 9 to 14 V
      Standard resistance
      Tester Connection Ignition switch Condition Specified Condition
      O1-1 (E1) - Body ground Always 10 kΩ or higher

    NG

    CHECK TRANSMISSION CONTROL MODULE POWER SOURCE CIRCUIT

    OK

  3. CHECK HARNESS AND CONNECTOR (TRANSMISSION CONTROL ECU - ECM)


    1. A01BE50E01

      Disconnect the B7 ECM connector.

    2. Disconnect the O3 TCM connector.

    3. Measure the resistance of the wire harness side connectors.

      Standard resistance
      Tester Connection Specified Condition
      B7-22 (CAN+) - O3-21 (CAN+) Below 1 Ω
      B7-21 (CAN-) - O3-22 (CAN-) Below 1 Ω
      B7-22 (CAN+) or O3-21 (CAN+) - Body ground 10 kΩ or higher
      B7-21 (CAN-) or O3-22 (CAN-) - Body ground 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS AND CONNECTOR

    OK

  4. CHECK IF DTC OUTPUT RECURS


    1. Clear the DTC Click here.

    2. Replace the TCM.

      Tech Tips

      Replace the TCM with a TCM from a normally functioning vehicle of the same model.

    3. Start the engine.

    4. Read the DTCs Click here.

      Result
      Display (DTC Output) Proceed to
      U0001/A2 A
      No DTC B

    B

    REPLACE TRANSMISSION CONTROL MODULE ASSEMBLY

    A

    REPLACE ECM