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Home >> Toyota >> 2021 >> Highlander LE, 4WD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 5 (Electronically Controlled Brake System (HV) - Diagnostic Codes (07 Of 11)) >> ELECTRONICALLY CONTROLLED BRAKE SYSTEM (for HV Model) >> DTC C1256-09: Accumulator Low Pressure Abnormality Component Failure [10/2021 - 11/2023] >> Procedure

DTC C1256-09: Accumulator Low Pressure Abnormality Component Failure [10/2021 - 11/2023]: 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 C1256-09 is output. A
      DTCs other than C1256-09 are output. B

    Result: 

    B 

    REPAIR CIRCUITS INDICATED BY OUTPUT DTCS. Refer to  DIAGNOSTIC TROUBLE CODE CHART [10/2021 - 11/2023] 

    Result: 

    A 

    See step  2

  2. INSPECT BRAKE BOOSTER WITH ACCUMULATOR PUMP ASSEMBLY 
    1. Turn the ignition switch off.
      GTY883272Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component without harness connected
      (Brake Booster with Accumulator Pump 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 A9 brake booster with accumulator pump 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
      1 (BM1) - 2 (GND1) Always 10 Ω or less

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE BRAKE BOOSTER WITH ACCUMULATOR PUMP ASSEMBLY. Refer to  REMOVAL [12/2019 - 10/2022]  , or refer to  REMOVAL [10/2022 - 11/2023] 

    Result: 

    OK 

    See step  3

  3. READ VALUE USING GTS (ACCUMULATOR PRESSURE) 
    1. Reconnect the A9 brake booster with accumulator pump assembly connector.
    2. Disconnect the A43 brake pedal stroke sensor assembly connector.
    3. Depress the brake pedal several times to operate the pump motor, then wait until it stops.
    4. After the pump motor stops, wait for 30 seconds, then check the drop in the accumulator pressure sensor output value and the state of the pump motor.

      Chassis > Brake Booster > Data List 

      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      ECB Motor Relay Motor relay operation request OFF / ON OFF: Relay off
      ON: Relay on      		 ECB: Electronically Controlled Brake System
      Accumulator Pressure Accumulator pressure output value Min.: 0.00 MPa
      Max.: 24.48 MPa      		 15.00 to 21.00 MPa (Pressure stable and pump motor stopped) When brake fluid is stored in the accumulator: Accumulator pressure changes in accordance with volume of fluid stored in the accumulator

      Chassis > Brake Booster > Data List 

      Tester Display
      ECB Motor Relay
      Accumulator Pressure

      Result

      Result Proceed to
      The drop in the accumulator pressure sensor output value is less than 2.50 MPa 30 seconds after the pump motor stops, and the pump motor does not operate within 30 seconds after the pump motor stops. A
      The drop in the accumulator pressure sensor output value is 2.50 MPa or more 30 seconds after the pump motor stops, or the pump motor operates within 30 seconds after the pump motor stops. B

    Result: 

    A 

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

    Result: 

    B 

    See step  4

  4. READ VALUE USING GTS (SERVO PRESSURE) 
    1. Turn the ignition switch off.
    2. Reconnect the A43 brake pedal stroke sensor assembly connector.
    3. Perform the Active Test and operate the linear solenoid (SLR) in the brake booster with master cylinder assembly.
    4. Check that the servo pressure output value does not increase when performing the Active Test.

      Chassis > Brake Booster > Active Test 

      Tester Display Measurement Item Control Range Restrict Condition Diagnostic Note
      ECB Solenoid (SLR) Linear solenoid reduction valve (SLR) Solenoid Start (Activate)
      Solenoid SLR
      (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
      Servo Pressure Pressure value of servo Min.: 0.00 MPa
      Max.: 24.48 MPa      		 Brake pedal released: 0.00 to 1.53 MPa Brake pedal is being depressed: Changes in proportion to the depression force of the brake pedal

      Chassis > Brake Booster > Active Test 

      Active Test Display
      ECB Solenoid (SLR)
      Data List Display
      Servo Pressure

      OK

      The servo pressure output value does not increase when performing the Active Test.

      HINT: 

      • If the servo pressure output value increases, an internal brake fluid leak in the brake booster with master cylinder assembly is suspected.
      • Perform the Active Test with the current set to maximum.

      Result

      Result Proceed to
      The servo pressure output value increases. A
      The servo pressure output value does not increase. B

    Result: 

    A 

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY. Refer to  REMOVAL [12/2019 - 10/2022]  , or refer to  REMOVAL [10/2022 - 11/2023] 

    Result: 

    B 

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER WITH ACCUMULATOR PUMP ASSEMBLY 

    for Brake Booster with Master Cylinder Assembly: Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

    for Brake Booster with Accumulator Pump Assembly: Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

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