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SFI SYSTEM, Diagnostic DTC:U0129, U1103

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DTC Code DTC Name
U0129 Lost Communication with Brake System Control Module
U1103 Lost Communication with Stop and Start Control Module
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DESCRIPTION

The ECM, brake actuator assembly (skid control ECU assembly) and engine stop and start ECU*1 communicate with each other via CAN communication. The ECUs also communicate with other computers through the ECM. If there is a problem with this communication, the ECM stores this DTC.

DTC No. DTC Detection Condition Trouble Area
U0129

Following conditions are met for 2 seconds (1 trip detection logic):


  • Ignition switch ON

  • Battery voltage 10.8 V or higher

  • No communication between ECM and skid control ECU

  • Brake actuator assembly (Skid control ECU assembly)

  • CAN communication system

  • ECM
U1103*1

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


  • Ignition switch ON

  • No communication between ECM and stop and start ECU

  • Wire harness (CANL and CANH circuits)

  • ECM

  • Engine stop and start ECU

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CAUTION / NOTICE / HINT

Tip:

  • When DTCs indicating a CAN communication system malfunction are output, repair the CAN communication system first.

  • If the CAN communication malfunctions, there is no data output from the ECM. In this case, some of the freeze frame data are not correct and not identical with the ECM data, however the ECM data are correct.

  • Read freeze frame data using the GTS. Freeze frame data records the engine condition when malfunctions are detected. 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.

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PROCEDURE


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    CHECK FOR ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC U0129 OR U1103)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Clear DTCs (Click here).

    5. Turn the ignition switch off and wait for at least 30 seconds.

    6. Turn the ignition switch to ON.

    7. Turn the GTS on.

    8. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

    9. Read DTCs.

      Table 1. Result
      Result Proceed to
      DTC U0129 or U1103 and other DTCs are output A
      DTC U0129 or U1103 is output

      B*1

      C*2

      • *1: w/ Toyota Safety Sense

      • *2: w/o Toyota Safety Sense

      Tip:

      If any DTCs other than U0129 or U1103 are output, troubleshoot those DTCs first.