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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 [10/2021 - 11/2023] >> Procedure

DTC C137B-A2: Brake System Control Module "A" System Voltage System Voltage Low [10/2021 - 11/2023]: Procedure

WARNING: This page is about a different variant/trim than selected.
  1. READ VALUE USING GTS (IG1 VOLTAGE, IG2 VOLTAGE AND +BS VOLTAGE) 
    1. Using the GTS, monitor the voltage values of IG1 voltage, IG2 voltage, and +BS voltage.

      Chassis > Brake/EPB > Data List 

      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      IG1 Voltage IG1 voltage value Min.: 0.000 V
      Max.: 20.000 V      		 - Changes in proportion to auxiliary battery voltage
      IG2 Voltage IG2 voltage value Min.: 0.000 V
      Max.: 20.000 V      		 - Changes in proportion to auxiliary battery voltage
      +BS Voltage +BS voltage value Min.: 0.000 V
      Max.: 20.000 V      		 - Changes in proportion to auxiliary battery voltage

      Chassis > Brake/EPB > Data List 

      Tester Display
      IG1 Voltage
      IG2 Voltage
      +BS Voltage

      Result

      Result Proceed to
      IG1 voltage value is below 11 V. A
      IG2 voltage value is below 11 V. B
      +BS voltage value is below 11 V. C
      IG1 voltage, IG2 voltage and +BS voltage values are below 11 V. D
      IG1 voltage, IG2 voltage and +BS voltage values are 11 to 14 V. E

    Result: 

    B 

    See step  5

    Result: 

    C 

    See step  6

    Result: 

    D 

    See step  7

    Result: 

    E 

    USE SIMULATION METHOD TO CHECK 

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

    Result: 

    A 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (IG1 TERMINAL) 
    1. Turn the ignition switch off.
      GTY848524Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to No. 2 Skid Control ECU (Brake Actuator Assembly))
    2. Make sure that there is no looseness at the locking part and the connecting part of the connectors.

      OK

      The connector is securely connected.

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

      OK

      No deformation or corrosion.

    5. Turn the ignition switch to ON.
    6. 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  3

  3. 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  4

  4. 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 [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

  5. CHECK HARNESS AND CONNECTOR (IG2 TERMINAL) 
    1. Turn the ignition switch off.
      GTY848525Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to No. 2 Skid Control ECU (Brake Actuator Assembly))
    2. Make sure that there is no looseness at the locking part and the connecting part of the connectors.

      OK

      The connector is securely connected.

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

      OK

      No deformation or corrosion.

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

      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: 

    OK 

    See step  3

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  6. 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. Make sure that there is no looseness at the locking part and the connecting part of the connectors.

      OK

      The connector is securely connected.

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

      OK

      No deformation or corrosion.

    5. 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: 

    OK 

    See step  3

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  7. CHECK HARNESS AND CONNECTOR (GND1 TERMINAL) 
    1. Turn the ignition switch off.
    2. Make sure that there is no looseness at the locking part and the connecting part of the connectors.

      OK

      The connector is securely connected.

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

      OK

      No deformation or corrosion.

    5. 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: 

    OK 

    See step  3

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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