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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 C12F8-12: ECB Solenoid Control "A" Circuit Short to Battery; DTC C12F8-14: ECB Solenoid Control "A" Circuit Short to Ground or Open [11/2023 - ] >> Procedure

DTC C12F8-12: ECB Solenoid Control "A" Circuit Short to Battery; DTC C12F8-14: ECB Solenoid Control "A" Circuit Short to Ground or Open [11/2023 - ]: Procedure

WARNING: This page is about a different variant/trim than selected.
  1. READ VALUE USING GTS (BS VOLTAGE) 
    1. Perform the Active Test and operate the main relay.
    2. Monitor the value of BS Voltage when the Active Test is being performed.

      Chassis > Brake Booster > Active Test 

      Tester Display Measurement Item Control Range Restrict Condition Diagnostic Note
      ECB Main Relay Main relay OFF / ON Vehicle condition: Vehicle stopped
      HINT: 
      To protect this Actuator and Solenoid, this test will only last 5 seconds.      		 ECB: Electronically Controlled Brake System

      Chassis > Brake Booster > Data List 

      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      BS Voltage BS voltage value Min.: 0.0 V
      Max.: 25.5 V      		 - Changes in proportion to auxiliary battery voltage

      Chassis > Brake Booster > Active Test 

      Active Test Display
      ECB Main Relay
      Data List Display
      BS Voltage

      Result

      Result Proceed to
      During the Active Test, the voltage indicated by BS Voltage increases to the approximate voltage of the auxiliary battery. A
      During the Active Test, the voltage indicated by BS Voltage remains low around 0 V. B

      HINT: 

      During the Active Test, the voltage indicated by BS Voltage changes in proportion to the voltage of the auxiliary battery.

    Result: 

    B 

    See step  4

    Result: 

    A 

    See step  2

  2. CLEAR DTC 
    1. Clear the DTCs.

      Chassis > Brake Booster > Clear DTCs 

    2. Turn the ignition switch off.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  3

  3. 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 Booster > Trouble Codes 

      Result

      Result Proceed to
      DTCs C12F8-12 and C12F8-14 are not output. A
      DTCs C12F8-12 and/or C12F8-14 are output. B

    Result: 

    A 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [12/2019 - ] 

    Result: 

    B 

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY. Refer to  REMOVAL [11/2023 - ] 

  4. CHECK HARNESS AND CONNECTOR (+BI TERMINAL) 
    1. Turn the ignition switch off.
      GTY895230Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to No. 1 Skid Control ECU (Brake Booster with Master Cylinder Assembly))
    2. Make sure that there is no looseness at the locking part and the connecting part of the connector.

      OK

      The connector is securely connected.

    3. Disconnect the A44 No. 1 skid control ECU (brake booster with master cylinder 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
      A44-14 (+BI1) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  5

  5. CHECK HARNESS AND CONNECTOR (BS TERMINAL) 
    1. Measure the voltage according to the value(s) in the table below.
      GTY895231Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to No. 1 Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      Standard Voltage

      Tester Connection Condition Specified Condition
      A44-15 (BS) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY. Refer to  REMOVAL [11/2023 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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