VEHICLE STABILITY CONTROL SYSTEM, Diagnostic DTC:C1256

DTC Code DTC Name
C1256 Accumulator Low Pressure

DESCRIPTION

Refer to DTC C1254 (Click here).

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

C1256

Accumulator Low Pressure

The fluid pressure inside the accumulator is below the standard value.

  • Brake booster with accumulator pump assembly

  • Master cylinder solenoid (Accumulator pressure sensor)

  • Hydraulic brake booster assembly

CAUTION / NOTICE / HINT

Note:

When replacing the master cylinder solenoid, perform calibration (Click here).

Tip:

When DTC C1251, C1253, or C1254 is output together with DTC C1256 inspect and repair the trouble area indicated by DTC C1251, C1253, or C1254 first.

PROCEDURE

  1. RECONFIRM DTC

    1. Clear the DTCs.

      Click hereClick here

      Chassis > ABS/VSC/TRC > Clear DTCs

    2. Turn the engine switch off.

    3. Depress the brake pedal 20 times or more.

    4. Turn the engine switch on (IG).

    5. Wait for 99 seconds.

    6. Check if the same DTC is output.

      Click hereClick here

      Chassis > ABS/VSC/TRC > Trouble Codes

      Result

      Result

      Proceed to

      DTC is output

      A

      DTC is not output

      B
      Tip:

      Excessive brake pedal operation results in abnormal accumulator pressure consumption. This is normal.

    B

    USE SIMULATION METHOD TO CHECK

    Click hereClick hereClick here

    A

  2. INSPECT HYDRAULIC BRAKE BOOSTER ASSEMBLY FUNCTION

    1. Inspect brake booster pump power supply system function.

      1. Turn the engine switch off.

      2. Depress the brake pedal 20 times or more to release the pressure in the accumulator.

        Tip:

        When the pressure is released, the brake pedal stroke becomes longer.

      3. Check that the brake fluid level is at the MAX level.

      4. Chock the 4 wheels and release the parking brake.

      5. Turn the engine switch on (IG) and measure the brake booster pump operating time (the time from when the brake booster pump starts operating until it stops).

        OK

        20 to 80 seconds

      6. Start the engine after the brake boost pump stops.

      7. Check that the ABS warning light and slip indicator light are not illuminated.

      8. Turn off the engine, and then turn the engine switch on (IG).

      9. Check that the brake boost pump operates and then stops when the brake pedal is depressed 4 or 5 times.

      10. Depress the brake pedal 4 or 5 times and measure the brake booster pump operating time (the time from when the brake booster pump starts operating until it stops).

        OK

        2 to 11 seconds

      11. Check that the brake warning light illuminates and the buzzer sounds when the brake pedal is fully depressed continuously 15 to 20 times.

        Note:

        Wait 120 seconds or more after turning the engine switch on (IG) before performing this inspection.

    2. Check brake booster operation.

      1. Turn the engine switch off.

      2. Depress the brake pedal 20 times or more to release the pressure in the accumulator.

        Tip:

        When the pressure is released, the brake pedal stroke becomes longer.

      3. Depress the brake pedal, start the engine, and check the change in the brake pedal height.

        OK

        The brake pedal moves slightly inward.

    3. Inspect brake master cylinder fluid pressure change.

      Click here

    Result

    Result

    OK

    NG
    NG

    INSPECT BRAKE BOOSTER PUMP ASSEMBLYClick here

    OK

  3. READ VALUE USING INTELLIGENT TESTER (ACCUMULATOR SENSOR)

    1. Connect the intelligent tester to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the intelligent tester on.

    4. Enter the following menus: Chassis / ABS/VSC/TRC / Data List.

      Chassis > ABS/VSC/TRC > Data List

      Tester Display

      Accumulator Sensor

      Chassis > ABS/VSC/TRC > Data List

      Tester Display

      Measurement Item

      Range

      Normal Condition

      Diagnostic Note

      Accumulator Sensor

      Accumulator pressure sensor reading

      Min.: 0.00 V, Max.: 5.00 V

      3.58 to 5 V

      If the value is constant regardless of the pump operation, an accumulator pressure sensor malfunction is suspected.

    5. Check that the accumulator output value is normal.

      OK

      Accumulator pressure sensor value is normal.

      Result

      Result

      OK

      NG
    NG

    REPLACE MASTER CYLINDER SOLENOID

    Click here

    OK

  4. RECONFIRM DTC

    1. Clear the DTCs.

      Click hereClick here

      Chassis > ABS/VSC/TRC > Clear DTCs

    2. Check if the same DTC is output.

      Click hereClick here

      Chassis > ABS/VSC/TRC > Trouble Codes

      Result

      Result

      Proceed to

      DTC is not output

      A

      DTC is output

      B
    A

    USE SIMULATION METHOD TO CHECK

    Click hereClick hereClick here

    B

    REPLACE MASTER CYLINDER SOLENOID

    Click here

  5. INSPECT BRAKE BOOSTER PUMP ASSEMBLY

    1. Remove the hydraulic brake booster assembly.

      Click here

    2. Using a screwdriver, remove the 2 screws and pull out the wire harness from the master cylinder solenoid.

    3. C173363C04

      *1

      Pump motor wire harness

      *a

      Red wire

      *b

      Black wire

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      Red wire terminal - Black wire terminal

      Always

      Below 2 Ω

    4. Install the pump motor wire harness to the master cylinder solenoid with the 2 screws.

    2.9 N*m

    30 kgf*cm

    26 in.*lbf

    Result

    Result

    OK

    NG
    OK

    REPLACE HYDRAULIC BRAKE BOOSTER ASSEMBLY

    Click here

    NG

    REPLACE BRAKE BOOSTER WITH ACCUMULATOR PUMP ASSEMBLY

    Click here