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 skid control ECU continues.

  • Skid control ECU branch wire or connector

  • Power source circuit of skid control ECU

  • Skid control ECU (Brake booster with master cylinder assembly)

Tech Tips

The diagnosis procedure is for when DTC U0129 is output by the power management control ECU (Intelligent tester display: Power Management2).

WIRING DIAGRAM

A003SI4E01

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. RECONFIRM DTC OUTPUT


    1. Reconfirm DTCs.

      Tech Tips

      If power management bus DTC U1002 is output from the power management control ECU (Intelligent tester display/Power Management2), troubleshoot for U1002 and check for malfunctions in the power management main bus circuit.

      Result
      Result Proceed to
      U1002 is not output from power management control ECU (Intelligent tester display/Power Management2) A
      U1002 is output from power management control ECU (Intelligent tester display/Power Management2) B

    B

    GO TO CIRCUITS INDICATED BY OUTPUT DTCS Click here

    A

  2. CHECK DTC (BRAKE SYSTEM)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the intelligent tester 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 DTCS Click here

    OK

  3. CHECK CAN BUS WIRE FOR DISCONNECTION (SKID CONTROL ECU)


    1. Turn the power switch off.

    2. A003UTKE49
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Skid Control ECU)

      Disconnect the skid control ECU connector.

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

      Standard Resistance
      Tester Connection Switch Condition Specified Condition
      A104-35 (CA2H) - A104-34 (CA2L) Power switch off 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 ASSEMBLY (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 ASSEMBLY (SKID CONTROL ECU) Click here