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

WIRING DIAGRAM

A01NGDCE06

INSPECTION PROCEDURE

Note


  • Turn the power switch off before measuring the resistances between CAN bus main wires and between CAN 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/PM2 Gateway), 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/PM2 Gateway) A
      U1002 is output from power management control ECU (Intelligent tester display/PM2 Gateway) B

    B

    GO TO CIRCUITS INDICATED BY OUTPUT DTCS Click here

    A

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


    1. Turn the power switch off.

    2. A01NDJ4E07
      Text in Illustration
      *1

      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
      A90-10 (CA2H) - A90-11 (CA2L) Power switch off 54 to 69 Ω

    NG

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

    OK

  3. CHECK HARNESS AND CONNECTOR (POWER SOURCE TERMINAL)


    1. Turn the power switch on (IG).

    2. A01NDJ4E12
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Skid Control ECU)

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A90-2 (IG1) - Body ground Power switch on (IG) 11 to 14 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

    OK

  4. CHECK FRONT AND SIDE MONITOR SYSTEM (GROUND TERMINAL)


    1. Turn the power switch off.

    2. Disconnect the skid control ECU connector.

    3. A01NFVOE01
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Skid Control ECU)

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A89-1 (GND) - Body ground Always Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (GROUND CIRCUIT)

    OK

    REPLACE SKID CONTROL ECU Click here