ELECTRONICALLY CONTROLLED BRAKE SYSTEM, Diagnostic DTC:C1256

DTC Code DTC Name
C1256 Accumulator Low Pressure

DESCRIPTION

The accumulator pressure sensor is built into the brake actuator (brake booster with master cylinder assembly) and detects the accumulator pressure.

The skid control ECU (brake booster with master cylinder assembly) turns on the brake warning light / red (malfunction) and brake warning light / yellow (minor malfunction), and sounds the meter buzzer if it senses a decrease in the accumulator pressure.

DTC C1256 may be stored if the accumulator pressure drops due to frequent braking (this is not a malfunction).

DTC No. Detection Item INF Code DTC Detection Condition Trouble Area Note
C1256 Accumulator Low Pressure

341

1125

Significant drop in accumulator pressure continues.

(DTCs will be stored and the buzzer will operate when either condition is met.)

  • Accumulator pressure dropped due to frequent brake pedal operation (not a malfunction)

  • Pump motor malfunction

  • Accumulator deterioration

  • Accumulator pressure sensor (brake booster with master cylinder assembly)

  • Supply voltage reduced

 Electronically controlled brake system DTC

WIRING DIAGRAM

Refer to DTCs C1252 and C1253.

Click here

CAUTION / NOTICE / HINT

Note


  • After replacing the skid control ECU (brake booster with master cylinder assembly), perform linear solenoid valve offset learning, ABS holding solenoid valve learning, yaw rate and acceleration sensor zero point calibration and system information memorization after performing "Reset Memory".

    Click here

  • Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE


  1. CHECK DTC


    1. Clear the DTCs.

      Click here


      Chassis > ABS/VSC/TRC > Clear DTCs

    2. Turn the power switch off.

    3. Turn the power switch on (IG).

    4. Check if the same DTC is output.

      Click here


      Chassis > ABS/VSC/TRC > Trouble Codes
      Result
      Result Proceed to
      DTC C1256 is output. A
      DTCs C1202, C1241, C1252, C1253 and/or C1391 are output. B

    B

    REPAIR CIRCUITS INDICATED BY OUTPUT DTCS Click here

    A

  2. INSPECT BRAKE BOOSTER PUMP ASSEMBLY


    1. A003KIFC04
      *a

      Component without harness connected

      (Brake Booster Pump Assembly)

      Turn the power switch off.

    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 A11 brake booster 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
      2 (BM1) - 4 (GND1) Always Below 10 Ω
      1 (BM2) - 3 (GND2) Always Below 10 Ω
      2 (BM1) - 1 (BM2) Always Below 1 Ω
      4 (GND1) - 3 (GND2) Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE BRAKE BOOSTER PUMP ASSEMBLY for LHD: Click here
    REPLACE BRAKE BOOSTER PUMP ASSEMBLY for RHD: Click here

    OK

  3. READ VALUE USING GTS (ACCUMULATOR PRESSURE)


    1. Reconnect the A11 brake booster pump assembly connector.

    2. Disconnect the A36 brake pedal stroke sensor assembly connector.

    3. Select the Data List on the GTS.

      Click here


      Chassis > ABS/VSC/TRC > Data List
      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      MT Voltage Value MT voltage value Min.: 0.00 V, Max.: 20.00 V

      Pump motor off: 0.00 V

      Pump motor on: 12.00 V

      		 -
      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 > ABS/VSC/TRC > Data List
      Tester Display
      MT Voltage Value
      Accumulator Pressure

    4. Depress the brake pedal several times to operate the pump motor, then wait until it stops.

    5. 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.

      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

    A

    USE SIMULATION METHOD TO CHECK Click here

    B

  4. READ VALUE USING GTS (SERVO PRESSURE)


    1. Turn the power switch off.

    2. Reconnect the A36 brake pedal stroke sensor assembly connector.

    3. Select the Active Test on the GTS.

      Click here


      Chassis > ABS/VSC/TRC > Active Test
      Tester Display Measurement Item Control Range Diagnostic Note
      ECB Solenoid (SLR) Linear solenoid reduction valve (SLR) Solenoid ON/OFF ECB: Electronically Controlled Brake System

      Chassis > ABS/VSC/TRC > Active Test
      Tester Display
      ECB Solenoid (SLR)

    4. Select the Data List on the GTS.

      Click here


      Chassis > ABS/VSC/TRC > 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 2.10 MPa Brake pedal is being depressed: Changes in proportion to the depression force of the brake pedal

      Chassis > ABS/VSC/TRC > Data List
      Tester Display
      Servo Pressure

    5. Perform the Active Test and operate the linear solenoid (SLR) in the brake actuator (brake booster with master cylinder assembly).

    6. Check that the servo pressure output value does not increase when performing the Active Test.

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

      Tech Tips

      If the servo pressure output value increases, an internal brake fluid leak in the brake actuator (brake booster with master cylinder assembly) is suspected.

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

    A

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY for LHD: Click here
    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY for RHD: Click here

    B

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER PUMP ASSEMBLY for the brake booster with master cylinder assembly (for LHD): Click here
    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER PUMP ASSEMBLY for the brake booster with master cylinder assembly (for RHD): Click here
    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER PUMP ASSEMBLY for the brake booster pump assembly (for LHD): Click here
    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER PUMP ASSEMBLY for the brake booster pump assembly (for RHD): Click here