DTC    C1256/57    Accumulator Low Pressure

for Preparation Click here


DESCRIPTION

The accumulator pressure sensor is built into the actuator and detects the accumulator pressure.
The skid control ECU turns on the brake control warning light and sounds the skid control buzzer if it senses a decrease in the accumulator pressure.

DTC No.
INF Code
DTC Detection Condition
Trouble Area
C1256/57
141
When either of the following is detected:
  1. When inputting the vehicle speed, the brake operation is input with the accumulator pressure decreased or the accumulator pressure extremely decreases while braking for 0.3 seconds or more.
  2. The accumulator pressure has been low since system start and the pressure is less than 14.62 MPa for 0.8 seconds. (After a condition is met, the code is stored and the buzzer sounds.)
  1. Brake actuator assembly
  2. Skid control ECU
↑
143
When 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 decreases without increasing the wheel cylinder pressure of each wheel.
  3. With the motor relay abnormal or off, the accumulator pressure is less than 14.62 MPa for 0.5 seconds or more.
↑

WIRING DIAGRAM

Refer to DTCs C1252/52 and C1253/53 (Click here).

INSPECTION PROCEDURE

NOTICE:
When replacing the skid control ECU or brake actuator assembly, perform initialization of linear solenoid valve and calibration (Click here).

HINT:
  1. When C1241/41, C1252/52 or C1253/53 are output together with C1256/57, inspect and repair the trouble areas indicated by C1241/41, C1252/52 or C1253/53 first.
  2. DTCs may be output if the accumulator pressure drops due to frequent braking (this is not a malfunction).

1.INSPECT BRAKE ACTUATOR ASSEMBLY


    C112750E01

  1. Disconnect the brake actuator assembly connector.

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

    Resistance:
    LHD:
    Tester Connection
    		Specified Condition
    A16-2 (BM1) - A16-31 (GND1)
    		Below 10 Ω
    A16-1 (BM2) - A16-31 (GND1)
    		Below 10 Ω
    A16-2 (BM1) - A16-1 (BM2)
    		Below 1 Ω
    A16-31 (GND1) - A16-32 (GND2)
    		Below 1 Ω
    A16-2 (BM1) - A16-33 (MTT)
    		About 33 Ω
    A16-1 (BM2) - A16-33 (MTT)
    		About 33 Ω

    Resistance:
    RHD:
    Tester Connection
    		Specified Condition
    A16-31 (BM1) - A16-1 (GND1)
    		Below 10 Ω
    A16-32 (BM2) - A16-1 (GND1)
    		Below 10 Ω
    A16-31 (BM1) - A16-32 (BM2)
    		Below 1 Ω
    A16-1 (GND1) - A16-2 (GND2)
    		Below 1 Ω
    A16-31 (BM1) - A16-3 (MTT)
    		About 33 Ω
    A16-32 (BM2) - A16-3 (MTT)
    		About 33 Ω



NG
REPLACE BRAKE ACTUATOR ASSEMBLY
OK


2.READ VALUE OF INTELLIGENT TESTER (ACCUMULATOR PRESSURE SENSOR)

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch on (IG).

  1. Select the DATA LIST mode on the intelligent tester.

    ABS / VSC / TR(A)C: 
    Item (Display)
    		Measurement Item /
    Range (Display)
    		Normal Condition
    Accumulator Sensor
    		Accumulator pressure sensor / min.: 0 V, max.: 5 V
    		Specified value: 2.6 to 3.8 V

  1. Depress the brake pedal 4 or 5 times to operate the pump motor, and check the output value on the intelligent tester with the motor stopped (not braking).

    OK:
    ACC pressure sensor's output voltage does not drop.



NG
REPLACE BRAKE ACTUATOR ASSEMBLY
OK


3.RECONFIRM DTC

  1. Clear the DTC (Click here).

  1. Turn the engine switch on (IG).

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

    HINT:
    Reinstall the sensors, connectors, etc. and restore the vehicle to its prior condition before rechecking for DTCs.


    Result:

    Condition
    		Proceed To
    DTC (C1256/57) is not output
    		A
    DTC (C1256/57) is output
    		B



B
REPLACE SKID CONTROL ECU
A

END