Dtc C1256 Accumulator Low Pressure

Brake. Land Cruiser. Urj200, 202 Grj200 Vdj200
Brake Control Dynamic Control Systems. Land Cruiser. Urj200, 202 Grj200 Vdj200

DESCRIPTION

INSPECTION PROCEDURE

RECONFIRM DTC

INSPECT HYDRAULIC BRAKE BOOSTER ASSEMBLY FUNCTION

READ VALUE USING GTS (ACCUMULATOR SENSOR)

RECONFIRM DTC

INSPECT BRAKE BOOSTER PUMP ASSEMBLY

DTC C1256 Accumulator Low Pressure


DESCRIPTION

Refer to DTC C1254 (Click here).

DTC Code
DTC Detection Condition
Trouble Area
C1256
The fluid pressure inside the accumulator is below the standard value.
  1. Brake booster with accumulator pump assembly
  2. Master cylinder solenoid (Accumulator pressure sensor)
  3. Hydraulic brake booster assembly

INSPECTION PROCEDURE

NOTICE:
After replacing the master cylinder solenoid, perform zero point calibration (Click here).
HINT:
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.
1.RECONFIRM DTC

  1. Clear the DTCs (Click here).

  1. Turn the ignition switch off.

  1. Depress the brake pedal 20 times or more.

  1. Turn the ignition switch to ON.

  1. Wait for 99 seconds.

  1. Check if the same DTC is output (Click here).

    Result
    Result
    		Proceed to
    DTC is output
    		A
    DTC is not output
    		B
    HINT:
    Excessive brake pedal operation results in abnormal accumulator pressure consumption. This is normal.


B
CHECK FOR INTERMITTENT PROBLEMS (Click here)
A


2.INSPECT HYDRAULIC BRAKE BOOSTER ASSEMBLY FUNCTION

  1. Inspect brake booster pump power supply system function.

    1. Turn the ignition switch off.

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

      HINT:
      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 ignition switch to ON 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 ignition switch to ON.

    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.

      NOTICE:
      Wait 120 seconds or more after turning the ignition switch to ON before performing this inspection.

  1. Check brake booster operation.

    1. Turn the ignition switch off.

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

      HINT:
      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.

  1. Inspect brake master cylinder fluid pressure change (for LHD: Click here, for RHD: Click here).



NG
Go to step 5
OK


3.READ VALUE USING GTS (ACCUMULATOR SENSOR)

  1. Connect the GTS to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the GTS on.

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


ABS/VSC/TRC
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.

  1. Check that the accumulator output value is normal.

    OK:
    Accumulator pressure sensor value is normal.
    Result
    Result
    		Proceed to
    OK
    		A
    NG (for LHD)
    		B
    NG (for RHD)
    		C


B
REPLACE MASTER CYLINDER SOLENOID (Click here)

C
REPLACE MASTER CYLINDER SOLENOID (Click here)
A


4.RECONFIRM DTC

  1. Clear the DTCs (Click here).

  1. Check if the same DTC is output (Click here).

    Result
    Result
    		Proceed to
    DTC is not output
    		A
    DTC is output (for LHD)
    		B
    DTC is output (for RHD)
    		C


B
REPLACE MASTER CYLINDER SOLENOID (Click here)

C
REPLACE MASTER CYLINDER SOLENOID (Click here)
A

CHECK FOR INTERMITTENT PROBLEMS (Click here)

5.INSPECT BRAKE BOOSTER PUMP ASSEMBLY

  1. Remove the hydraulic brake booster assembly (for LHD: Click here, for RHD: Click here).

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



    Land Cruiser. Urj200, 202 Grj200 Vdj200.Brake Control Dynamic Control Systems.Anti-Lock Brake System. Dtc C1256 Accumulator Low Pressure

  1. 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
    Text in Illustration
    *1
    		Pump motor wire harness
    *a
    		Red wire
    *b
    		Black wire

  1. Install the pump motor wire harness to the master cylinder solenoid with the 2 screws (for LHD: Click here, for RHD: Click here).

Result
Result
Proceed to
OK (for LHD)
A
OK (for RHD)
B
NG (for LHD)
C
NG (for RHD)
D


B
REPLACE HYDRAULIC BRAKE BOOSTER ASSEMBLY (Click here)

C
REPLACE BRAKE BOOSTER WITH ACCUMULATOR PUMP ASSEMBLY (Click here)

D
REPLACE BRAKE BOOSTER WITH ACCUMULATOR PUMP ASSEMBLY (Click here)
A

REPLACE HYDRAULIC BRAKE BOOSTER ASSEMBLY (Click here)