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Home >> Toyota >> 2021 >> Highlander LE, 4WD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 37 (Electronically Controlled Brake System (HV) - Diagnostic Codes (08 Of 11)) >> ELECTRONICALLY CONTROLLED BRAKE SYSTEM (for HV Model) >> DTC C137B-A2: Brake System Control Module "A" System Voltage System Voltage Low [11/2023 - ] >> Procedure

DTC C137B-A2: Brake System Control Module "A" System Voltage System Voltage Low [11/2023 - ]: Procedure

WARNING: This page is about a different variant/trim than selected.
  1. CHECK HARNESS AND CONNECTOR (IG1 TERMINAL) 
    1. Make sure that there is no looseness at the locking part and the connecting part of the connectors.
      GTY848524Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to No. 2 Skid Control ECU (Brake Actuator Assembly))

      OK

      The connector is securely connected.

    2. Disconnect the A57 No. 2 skid control ECU (brake actuator assembly) connector.
    3. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

    4. Turn the ignition switch to ON.
    5. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A57-45 (IG1) - Body ground Ignition switch ON 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (IG2 TERMINAL) 
    1. Measure the voltage according to the value(s) in the table below.
      GTY848525Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to No. 2 Skid Control ECU (Brake Actuator Assembly))

      Standard Voltage

      Tester Connection Condition Specified Condition
      A57-15 (IG2) - Body ground Ignition switch ON 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (+BS TERMINAL) 
    1. Turn the ignition switch off.
      GTY848560Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to No. 2 Skid Control ECU (Brake Actuator Assembly))
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A57-14 (+BS) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

  4. CHECK HARNESS AND CONNECTOR (GND1 TERMINAL) 
    1. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A57-1 (GND1) - Body ground 1 minute or more after disconnecting the cable from the negative (-) auxiliary battery terminal Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  5

  5. CLEAR DTC 
    1. Reconnect the A57 No. 2 skid control ECU (brake actuator assembly) connector.
    2. Clear the DTCs.

      Chassis > Brake/EPB > Clear DTCs 

    3. Turn the ignition switch off.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  6

  6. RECONFIRM DTC 
    1. Based on the Freeze Frame Data and interview with the customer, attempt to reproduce the conditions when the malfunction occurred.
    2. Check if the same DTC is output.

      Chassis > Brake/EPB > Trouble Codes 

      Result

      Result Proceed to
      DTC C137B-A2 is not output. A
      DTC C137B-A2 is output. B

    Result: 

    A 

    USE SIMULATION METHOD TO CHECK 

    Refer to HOW TO PROCEED WITH TROUBLESHOOTING [12/2019 - ]

    Result: 

    B 

    REPLACE BRAKE ACTUATOR ASSEMBLY 

    Refer to REMOVAL [11/2023 - ]

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