CAN COMMUNICATION SYSTEM, Diagnostic DTC:U0129

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

DESCRIPTION

DTC No. DTC Detection Condition Trouble Area
U0129 No communication from the brake booster with master cylinder (skid control ECU) continues.

  • Brake booster with master cylinder (Skid control ECU) branch wire or connector

  • Power source circuit of brake booster with master cylinder (skid control ECU)

  • Brake booster with master cylinder (Skid control ECU)

Tech Tips

The diagnosis procedure is for when DTC U0129 is output by the power management control ECU (GTS display: Hybrid Control).

WIRING DIAGRAM

A0040DHE03

INSPECTION PROCEDURE

Note


  • Turn the power switch off before measuring the resistances between CAN main bus wires and between CAN main bus branch wires.

  • Turn the power switch off before inspecting CAN bus wires for a ground short.

  • After the power switch is turned off, check that the key reminder warning system and light reminder warning system are not operating.

  • Before measuring the resistance, leave the vehicle as is for at least 1 minute and do not operate the power switch, any other switches or the doors. If any doors need to be opened in order to check connectors, open the doors and leave them open.

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. CHECK DTC (BRAKE SYSTEM)


    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.

      OK
      DTC C1241 is not output.

    NG

    GO TO CIRCUITS INDICATED BY OUTPUT DTC Click here

    OK

  2. RECONFIRM DTC OUTPUT


    1. Check if Hybrid Control of the power management control ECU outputs only DTC U0129.

      Tech Tips

      If the power management control ECU outputs DTC U0100 and DTC U0129, check the branch circuit of the power management bus.

      Result
      Result Proceed to

      The power management control ECU outputs only DTC U0129.

      (GTS display: Hybrid Control)

      		 A

      The power management control ECU 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 WIRES (SKID CONTROL ECU BRANCH WIRE)


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

    2. A0041ILE05
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Brake Booster with Master Cylinder (Skid Control ECU))

      Disconnect the A57 brake booster with master cylinder (skid control ECU) connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A57-35 (CA2H) - A57-34 (CA2L) 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

    B

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER (SKID CONTROL ECU) Click here

    C

    REPAIR OR REPLACE CAN BUS BRANCH WIRE OR CONNECTOR (SKID CONTROL ECU BRANCH WIRE)

    A

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER (SKID CONTROL ECU) Click here