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Home >> Toyota >> 2021 >> Mirai Limited >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Electronically Controlled Brake System - Diagnostic Codes (2 Of 4) >> Electronically Controlled Brake System >> DTC C1256-00: Accumulator Low Pressure Abnormality [11/2020 - ] >> Procedure

DTC C1256-00: Accumulator Low Pressure Abnormality [11/2020 - ]: Procedure

  1. CHECK DTC 
    1. Check the DTCs that are output.

      Chassis > Brake Booster > Trouble Codes 

      Result

      Result Proceed to
      Only C1256-00 is output A
      C1256-00 and other DTCs are output B

    Result: 

    B 

    REPAIR CIRCUITS INDICATED BY OUTPUT DTCS 

    Result: 

    A 

    See step  2

  2. CHECK DTC 
    1. Check the DTCs that are output.

      Chassis > Brake/EPB > Trouble Codes 

      Result

      Result Proceed to
      DTCs are not output A
      DTCs are output B

    Result: 

    B 

    REPAIR CIRCUITS INDICATED BY OUTPUT DTCS 

    Result: 

    A 

    See step  3

  3. INSPECT BRAKE BOOSTER PUMP ASSEMBLY 

    Pre-procedure1

    • Turn the ignition switch off.
    • Inspect the brake booster pump assembly.

      Refer to INSPECTION [11/2020 - ]

      OK

      The brake booster pump assembly is normal.

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • None

    Result: 

    NG 

    REPLACE BRAKE BOOSTER PUMP ASSEMBLY. Refer to  REMOVAL [11/2020 - 11/2021]  , or refer to  REMOVAL [11/2021 - 12/2022]  , or refer to  REMOVAL [12/2022 - 12/2023]  , or refer to  REMOVAL [12/2023 - ] 

    Result: 

    OK 

    See step  4

  4. READ VALUE USING GTS (MOTOR RELAY AND ACCUMULATOR PRESSURE) 

    Pre-procedure1

    • Reconnect the A39 brake booster pump assembly connector.
    • Disconnect the A2 brake pedal stroke sensor assembly connector.
    • Depress the brake pedal several times to operate the pump motor, then wait until it stops.
    • 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

    Post-procedure1

    • None

    Result: 

    A 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2020 - ] 

    Result: 

    B 

    See step  5

  5. READ VALUE USING GTS (SERVO PRESSURE) 

    Pre-procedure1

    • Turn the ignition switch off.
    • Reconnect the A2 brake pedal stroke sensor assembly connector.
    • Perform the Active Test and operate the linear solenoid (SLR) in the brake booster with master cylinder assembly.
    • 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
      • Check that park (P) is selected
      • 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

    Post-procedure1

    • None

    Result: 

    A 

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY. Refer to  REMOVAL [11/2020 - 11/2021]  , or refer to  REMOVAL [11/2021 - 12/2022]  , or refer to  REMOVAL [12/2022 - 12/2023]  , or refer to  REMOVAL [12/2023 - ] 

    Result: 

    B 

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

    for Brake Booster with Master Cylinder Assembly: Refer to REMOVAL [11/2020 - 11/2021] , or refer to REMOVAL [11/2021 - 12/2022] , or refer to REMOVAL [12/2022 - 12/2023] , or refer to REMOVAL [12/2023 - ]

    for Brake Booster Pump Assembly: Refer to REMOVAL [11/2020 - 11/2021] , or refer to REMOVAL [11/2021 - 12/2022] , or refer to REMOVAL [12/2022 - 12/2023] , or refer to REMOVAL [12/2023 - ]

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