ELECTRONICALLY CONTROLLED BRAKE SYSTEM, Diagnostic DTC:C1256/57

DTC Code DTC Name
C1256/57 Accumulator Low Pressure

DESCRIPTION

The accumulator pressure sensor is built into the brake actuator assembly and detects the accumulator pressure.

The skid control ECU 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 C1256/57 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
C1256/57 Accumulator Low Pressure

141

143

  • INF Code: 141


    • Either of the following is detected:


      1. When inputting the vehicle speed, the brake operation is input with the accumulator pressure low or the accumulator pressure extremely decreased while braking for 0.3 seconds or more.

      2. The accumulator pressure has been low since system start and pressure is less than 14.62 MPa (149.1 kgf/cm2, 2121 psi) for 0.8 seconds or more.

        (Stores the DTC after the conditions are met, and sounds buzzer.)

  • INF Code: 143


    • Any of the following is detected:


      1. When inputting the vehicle speed, any of the wheel cylinder pressure sensor values is lower than the specified value with the accumulator pressure low for 0.5 seconds or more.

      2. The accumulator pressure decreased without increasing the wheel cylinder pressure of each wheel.

      3. With the ABS motor relay abnormal or off, the accumulator pressure is less than 14.62 MPa (149.1 kgf/cm2, 2121 psi) for 0.5 seconds or more.

  • INF Code: 141


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

    • Pump motor malfunction

    • Accumulator deterioration

    • Brake fluid leaks

    • Accumulator pressure sensor

    • Supply voltage reduced

  • INF Code: 143


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

    • Pump motor malfunction

    • Accumulator deterioration

    • Accumulator pressure sensor

    • Supply voltage reduced

 Electronically controlled brake system DTC

WIRING DIAGRAM

Refer to DTCs C1252/52 and C1253/53.

Click here

CAUTION / NOTICE / HINT

Note

When replacing the brake actuator assembly, perform initialization and calibration of the linear solenoid valve.

Click here

Tech Tips

When C1202/68, C1241/41, C1252/52, C1253/53 and/or C1391/69 are output together with C1256/57, inspect and repair the trouble areas indicated by C1202/68, C1241/41, C1252/52, C1253/53 and/or C1391/69 first.

for C1202/68: Click here

for C1241/41: Click here

for C1252/52 and C1253/53: Click here

for C1391/69: Click here

PROCEDURE


  1. BRAKE PROBLEM CHECK


    1. Ask the customer if frequent braking was performed while the brake warning light / yellow (minor malfunction) was on.

      Result
      Result Proceed to
      Frequent braking was not performed. A
      Frequent braking was performed. B

      Tech Tips

      This DTC may be stored even if the accumulator pressure drops only temporarily due to frequent braking.


    B

    END

    A

  2. INSPECT BRAKE ACTUATOR ASSEMBLY


    1. Make sure that there is no looseness at the locking part and the connecting part of the connector.

      A0022C2C01
      *A for LHD *B for RHD
      *a

      Component without harness connected

      (Brake Actuator Assembly)

      		 - -

    2. Disconnect the A16 brake actuator assembly connector.

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

      Standard Resistance
      for LHD
      Tester Connection Condition Specified Condition
      2 (BM1) - 31 (GND1) Always Below 1 Ω
      1 (BM2) - 32 (GND2) Always Below 1 Ω
      2 (BM1) - 33 (MTT) Always 950 to 1050 Ω
      1 (BM2) - 33 (MTT) Always 950 to 1050 Ω
      for RHD
      Tester Connection Condition Specified Condition
      31 (BM1) - 1 (GND1) Always Below 1 Ω
      32 (BM2) - 2 (GND2) Always Below 1 Ω
      31 (BM1) - 3 (MTT) Always 950 to 1050 Ω
      32 (BM2) - 3 (MTT) Always 950 to 1050 Ω
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE BRAKE ACTUATOR ASSEMBLY for LHD: Click here
    REPLACE BRAKE ACTUATOR ASSEMBLY for RHD: Click here

    OK

  3. READ VALUE USING GTS (ACCUMULATOR PRESSURE SENSOR)


    1. Reconnect the A16 brake actuator assembly connector.

    2. Connect the GTS to the DLC3.

    3. Turn the power switch on (IG).

    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
      Accumulator Sensor Accumulator pressure sensor Min.: 0.00 V, Max.: 5.00 V Specified value: 2.60 to 3.80 V 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
      Accumulator Sensor

    5. Depress the brake pedal 4 or 5 times and operate the pump motor.

    6. Wait for 30 seconds without depressing the brake pedal.

    7. Check that the accumulator pressure sensor output value change is within the specified range.

      OK
      Accumulator pressure sensor output value change is less than 0.20 V.
      Result
      Proceed to
      OK
      NG

    OK

    USE SIMULATION METHOD TO CHECK Click here

    NG

    REPLACE BRAKE ACTUATOR ASSEMBLY for LHD: Click here
    REPLACE BRAKE ACTUATOR ASSEMBLY for RHD: Click here