SFI SYSTEM, Diagnostic DTC:U0129

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

DESCRIPTION

The Controller Area Network (CAN) is a serial data communication system for real time applications. This is a vehicle multiplex communication system which has a high communication speed (500 kbps) and a high level of ability to detect malfunctions. By pairing the CANH and CANL bus wires, the communication on the CAN is performed using the voltage differential between the wires.

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 more

  • No communication between ECM and skid control ECU

  • Brake actuator assembly (Skid control ECU assembly)

  • CAN communication system

  • ECM

CAUTION / NOTICE / HINT

Tech Tips


  • 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 intelligent tester. 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.

PROCEDURE


  1. CHECK FOR DTC (DTC U0129)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester 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 tester on.

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

    9. Read DTCs.

      Result
      Result Proceed to
      DTC U0129 is output A
      DTC is not output B

    A

    GO TO CAN COMMUNICATION SYSTEM Click here

    B

    CHECK FOR INTERMITTENT PROBLEMS Click here