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Home >> Toyota >> 2021 >> Highlander LE, 4WD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 65 (Electronically Controlled Brake System (HV) - Diagnostic Codes (10 Of 11)) >> ELECTRONICALLY CONTROLLED BRAKE SYSTEM (for HV Model) >> DTC C14C9-A2: Electronic Brake Booster Control Module "A" System Voltage Low [12/2019 - 10/2021] >> Procedure

DTC C14C9-A2: Electronic Brake Booster Control Module "A" System Voltage Low [12/2019 - 10/2021]: Procedure

WARNING: This page is about a different variant/trim than selected.
  1. CHECK DTC 
    1. Check the DTCs that are output.

      Chassis > Brake Booster > Trouble Codes 

      Chassis > Brake/EPB > Trouble Codes 

      Result

      Result Proceed to
      Only DTC C14C9-A2 is output. A
      DTCs other than C14C9-A2 are output. B

    Result: 

    B 

    REPAIR CIRCUITS INDICATED BY OUTPUT DTCS. Refer to  DIAGNOSTIC TROUBLE CODE CHART [12/2019 - 10/2021] 

    Result: 

    A 

    See step  2

  2. READ VALUE USING GTS (+BI1 VOLTAGE) 
    1. Drive the pump motor by performing the Active Test.

      HINT: 

      • The pump motor can be driven by performing the Active Test for ECB* solenoid (SLA).

        *: Electronically Controlled Brake System

      • Perform the Active Test with the current set to maximum.
    2. Monitor the value of Data List item +BI1 Voltage when the pump motor is being driven.

      Chassis > Brake Booster > Active Test 

      Tester Display Measurement Item Control Range Restrict Condition Diagnostic Note
      ECB Solenoid (SLA) Linear solenoid addition valve (SLA) Solenoid Start (Activate)
      Solenoid SLA
      (It is possible to set the current)      		 Vehicle condition:
      • Vehicle stopped
      • Shift lever is in P
      • Apply the parking brake
      		 ECB: Electronically Controlled Brake System

      Chassis > Brake Booster > Data List 

      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      BI Voltage +BI1 voltage value Min.: 0.000 V
      Max.: 20.000 V      		 - Changes in proportion to auxiliary battery voltage

      Chassis > Brake Booster > Active Test 

      Active Test Display
      ECB Solenoid (SLA)
      Data List Display
      BI Voltage

      Result

      Result Proceed to
      +BI1 voltage is 11 to 14 V. A
      +BI1 voltage is below 11 V. B

    Result: 

    A 

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

    Result: 

    B 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (+BI1 AND MRI1 TERMINAL) 
    1. Turn the ignition switch off.
      GTY895249Courtesy 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
      A44-1 (MRI1) - Body ground Always 11 to 14 V

      Result

      Result Proceed to
      11 to 14 V. A
      Below 11 V. B

    Result: 

    A 

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY. Refer to  REMOVAL [12/2019 - 10/2022] 

    Result: 

    B 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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