ELECTRONICALLY CONTROLLED BRAKE SYSTEM, Diagnostic DTC:C1256/56

DTC Code DTC Name
C1256/56 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 C1256/56 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

C1256/56

Accumulator Low Pressure

341

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 C1252/52 and C1253/53.

Click here

CAUTION / NOTICE / HINT

Note:

  • When replacing the brake actuator (brake booster with master cylinder assembly), perform initialization and calibration of the linear solenoid valve.

    Click here

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

Tip:

When C1202/68, C1241/41, C1252/52, C1253/53 and/or C1391/69 are output together with C1256/56, 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
      Tip:

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

    B

    END

    A

  2. INSPECT BRAKE BOOSTER PUMP ASSEMBLY

    1. C243137C27

      *a

      Component without harness connected

      (Brake Booster Pump Assembly)

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

    2. Disconnect the A103 and A104 brake booster pump assembly connectors.

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      A103-1 (BM1) - A103-2 (GND1)

      Always

      Below 10 Ω

      A104-2 (BM2) - A104-1 (GND2)

      Always

      Below 10 Ω

      A103-1 (BM1) - A104-2 (BM2)

      Always

      Below 1 Ω

      A103-2 (GND1) - A104-1 (GND2)

      Always

      Below 1 Ω

    Result

    Proceed to

    OK

    NG
    NG

    REPLACE BRAKE BOOSTER PUMP ASSEMBLY

    Click here

    OK

  3. READ VALUE USING GTS (ACCUMULATOR PRESSURE SENSOR)

    1. Reconnect the A103 and A104 brake booster pump assembly connectors.

    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: 2.90 to 4.20 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 to 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 0.55 V.

    Result

    Proceed to

    OK

    NG
    OK

    USE SIMULATION METHOD TO CHECK

    Click hereClick hereClick here

    NG

  4. PERFORM ACTIVE TEST USING GTS (SOLENOID VALVE)

    1. 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 (SMC/SRC/SCC)

      Switching solenoid valve (SMC/SRC/SCC)

      Solenoid ON/OFF

      • Operation sound of solenoid (clicking sound) can be heard

      • ECB: Electronically Controlled Brake System

      Chassis > ABS/VSC/TRC > Active Test

      Tester Display

      ECB Solenoid (SMC/SRC/SCC)
      Tip:

      The Active Test can be performed when the following conditions are met.

      • ABS main relay is on.

      • Shift lever is in P.

      • Parking brake is applied.

      • Vehicle speed is 0 km/h (0 mph).

    2. Perform the Active Test of the solenoid using the GTS.

    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

      Wheel Cylinder Pressure Sensor

      Wheel cylinder pressure sensor

      Min.: 0.00 V, Max.: 5.00 V

      Brake pedal released: 0.10 to 0.90 V

      Reading increases when brake pedal is depressed

      Chassis > ABS/VSC/TRC > Data List

      Tester Display

      Wheel Cylinder Pressure Sensor

    4. Check that the output value of the wheel cylinder pressure sensor does not increase.

      OK

      The output value of the wheel cylinder pressure sensor does not increase.

      Tip:

      If the output value increases, there may be brake fluid leaks in the brake actuator.

    Result

    Proceed to

    OK

    NG
    OK

    REPLACE BRAKE BOOSTER PUMP ASSEMBLY

    Click here

    NG

    REPLACE BRAKE BOOSTER PUMP ASSEMBLY

    for LHD:Click here

    for RHD:Click here