CAN COMMUNICATION SYSTEM, Diagnostic DTC:U0129

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

DESCRIPTION

DTC No. Detection Item DTC Detection Condition Trouble Area Note
U0129 Lost Communication with Brake System Control Module No communication from the skid control ECU assembly continues.

  • Skid control ECU assembly branch line or connector

  • Power source circuit of skid control ECU assembly

  • Skid control ECU assembly ground circuit

  • Skid control ECU assembly

Tech Tips

As there is no sub bus monitor ECU for sub bus 15, each ECU detects communication stops and stores DTCs.

Tech Tips

This diagnosis procedure is for when DTC U0129 is output only by the hybrid vehicle control ECU assembly (GTS display: Hybrid Control).

WIRING DIAGRAM

A01MST8E09
A01MST8E10

CAUTION / NOTICE / HINT

Note


  • Before measuring the resistance of the CAN bus, turn the power switch off and leave the vehicle for 1 minute or more without operating the key or any switches, or opening or closing the doors. After that, disconnect the cable from the negative (-) auxiliary battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.

  • After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work.

    Click here

  • Because the order of diagnosis is important to allow correct diagnosis, make sure to begin troubleshooting using How to Proceed with Troubleshooting when CAN communication system related DTCs are output.

    Click here

  • After the repair, perform the CAN bus check and check that all the ECUs and sensors connected to the CAN communication system are displayed.

    Click here

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

Tech Tips


  • Operating the power switch, any other switches or a door triggers related ECU and sensor communication on the CAN. This communication will cause the resistance value to change.

  • Even after DTCs are cleared, if a DTC is stored again after driving the vehicle for a while, the malfunction may be occurring due to vibration of the vehicle. In such a case, wiggling the ECUs or wire harness while performing the inspection below may help determine the cause of the malfunction.

PROCEDURE


  1. RECONFIRM DTC OUTPUT


    1. Connect the GTS to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the GTS on.

    4. Enter the following menus: Chassis / ABS/VSC/TRC / Trouble Codes.


      Chassis > ABS/VSC/TRC > Trouble Codes
      OK
      DTC C1242 is not output.
      Result
      Result
      OK
      NG

    NG

    GO TO DIAGNOSIS PROCEDURE INDICATED BY OUTPUT DTC Click here

    OK

  2. RECONFIRM DTC OUTPUT


    1. Reconfirm DTCs.


      Powertrain > Hybrid Control > Trouble Codes

      Tech Tips

      If the hybrid vehicle control ECU assembly outputs DTC U0100 and DTC U0129, check the branch circuit of sub bus 15.

      Result
      Result Proceed to

      The hybrid vehicle control ECU assembly outputs only DTC U0129.

      (GTS display: Hybrid Control)

      		 A

      The hybrid vehicle control ECU assembly outputs DTC U0100 and U0129.

      (GTS display: Hybrid Control)

      		 B

    B

    GO TO DIAGNOSIS PROCEDURE INDICATED BY OUTPUT DTC Click here

    A

  3. CHECK FOR OPEN IN CAN BUS LINES (SKID CONTROL ECU ASSEMBLY BRANCH LINE)


    1. Disconnect the cable from the negative (-) auxiliary battery terminal.

    2. Disconnect the A25 skid control ECU assembly connector.

    3. A0020TAC16
      *a

      Front view of wire harness connector

      (to Skid Control ECU Assembly)

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A25-9 (CANH) - A25-8 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 54 to 69 Ω
      Result
      Result Proceed to
      OK (for LHD) A
      OK (for RHD) B
      NG C

    A

    REPLACE SKID CONTROL ECU ASSEMBLY Click here

    B

    REPLACE SKID CONTROL ECU ASSEMBLY Click here

    C

    REPAIR OR REPLACE CAN BRANCH LINE OR CONNECTOR (SKID CONTROL ECU ASSEMBLY)