ECD SYSTEM(w/ DPF), Diagnostic DTC:U0129

DTC Code DTC Name
U0129 Lost Communication with Brake System Control Module

DESCRIPTION

The ECM and skid control ECU (brake actuator assembly) communicate with each other via the CAN communication line.

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

U0129
DTC Detection Drive Pattern DTC Detection Condition Trouble Area
Ignition switch ON

All of following conditions met for 1 second or more:


  • Ignition switch ON

  • +B terminal voltage 8 V or higher

  • No communication between ECM and skid control ECU

    (1 trip detection logic)

  • Wire harness (CANL and CANH circuits)

  • ECM

  • Skid control ECU (brake actuator assembly)

WIRING DIAGRAM

B0046ZDE01

CAUTION / NOTICE / HINT

Tech Tips


  • When a DTC indicating a CAN communication system malfunction is output, repair the CAN communication system before repairing each corresponding sensor.

  • 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, and other data from the time the malfunction occurred.

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

PROCEDURE


  1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC U0129)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Enter the following menus: System Select / Health Check.

    5. Read the DTCs.

      Result
      Result Proceed to
      DTC U0129 and other DTCs are output A
      DTC U0129 is output (w/ Toyota Safety Sense) B
      DTC U0129 is output (w/o Toyota Safety Sense) C

      Tech Tips

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


    A

    GO TO DTC CHART Click here

    B

    GO TO CAN COMMUNICATION SYSTEM Click here

    C

    GO TO CAN COMMUNICATION SYSTEM Click here