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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 C0594-00: Brake Booster Motor "A" Performance [11/2020 - ] >> Procedure

DTC C0594-00: Brake Booster Motor "A" Performance [11/2020 - ]: Procedure

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

      Chassis > Brake Booster > Trouble Codes 

      Result

      Result Proceed to
      Only C0594-00 is output A
      C0594-00 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. READ VALUE USING GTS (MOTOR RELAY) 
    1. Depress the brake pedal several times and check the operation status of the motor relay.

      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

      Chassis > Brake Booster > Data List 

      Tester Display
      ECB Motor Relay

      HINT: 

      Depressing the brake pedal several times drops the accumulator pressure and operates the pump motor.

      Result

      Result Proceed to
      The status of motor relay in the Data List turns on and off after depressing the brake pedal several times. A
      The status of motor relay in the Data List does not change even after depressing the brake pedal several times. B

    Result: 

    B 

    See step  10

    Result: 

    A 

    See step  4

  4. 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  5

  5. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - BRAKE BOOSTER PUMP ASSEMBLY) 
    • Make sure that there is no looseness at the locking part and the connecting part of the connector.

      OK

      The connector is securely connected.

    Pre-procedure1

    • Disconnect the A5 No. 1 skid control ECU (brake booster with master cylinder assembly) connector.
    • Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      A39-2 (GND1) or A5-30 (M-) - Body ground Always 10 kΩ or higher kΩ

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • None

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  6

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

    Pre-procedure1

    • Reconnect the A39 brake booster pump assembly connector.
    • Reconnect the A5 No. 1 skid control ECU (brake booster with master cylinder 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

      HINT: 

      • This inspection checks whether an accumulator pressure sensor malfunction, internal brake booster with master cylinder assembly leak or prolonged operation due to detection of low pressure caused by accumulator deterioration, caused the DTC to be stored.
      • If the brake fluid level in the brake master cylinder reservoir assembly drops, an external brake fluid leak is suspected.

      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: 

    B 

    See step  9

    Result: 

    A 

    See step  7

  7. CLEAR DTC 

    Pre-procedure1

    • Turn the ignition switch off.
    • Reconnect the A2 brake pedal stroke sensor assembly connector.
    • Clear the DTCs.

      Chassis > Brake Booster > Clear DTCs 

      Result

      Proceed to
      NEXT

    Post-procedure1

    • Turn the ignition switch off.

    Result: 

    NEXT 

    See step  8

  8. RECONFIRM DTC 

    Pre-procedure1

    • Based on the Freeze Frame Data and interview with the customer, attempt to reproduce the conditions when the malfunction occurred.
    • Check if the same DTC is output.

      Chassis > Brake Booster > Trouble Codes 

      Result

      Result Proceed to
      C0594-00 is not output A
      C0594-00 is output B

    Post-procedure1

    • None

    Result: 

    A 

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

    Result: 

    B 

    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 - ] 

  9. 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 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 - ] 

  10. CHECK HARNESS AND CONNECTOR (MRI1 TERMINAL) 

    Pre-procedure1

    • Turn the ignition switch off.
    • Make sure that there is no looseness at the locking part and the connecting part of the connector.

      OK

      The connector is securely connected.

    Pre-procedure2

    • Disconnect the A5 No. 1 skid control ECU (brake booster with master cylinder assembly) connector.
    • Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      A5-1 (MRI1) - Body ground Always 11 to 14 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • None

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  11

  11. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - BRAKE BOOSTER PUMP ASSEMBLY) 
    • Make sure that there is no looseness at the locking part and the connecting part of the connector.

      OK

      The connector is securely connected.

    Pre-procedure1

    • Disconnect the A39 brake booster pump assembly connector.
    • Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      A5-29 (M+) - A39-1 (BM1) Always Below 1 Ω Ω
      A5-29 (M+) or A39-1 (BM1) - Body ground Always 10 kΩ or higher kΩ

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • None

    Result: 

    OK 

    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: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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