RX400h · Service Manual BRAKE

C1256/57

Diagnostic trouble codes

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 Detecting Condition
 Trouble Area
C1256/57
 141
  1. Braking operation is input when accumulator pressure is less than 12.45 MPa and vehicle speed is input (detected value changes if accumulator pressure is low after system start).
  2. Accumulator pressure is less than 14.62 MPa for 120 sec. (changes according to power source voltage) after system start (stores the DTC after the conditions are met, and drives buzzer).
  1. Brake actuator assembly (accumulator pressure, accumulator pressure sensor, pump motor)
  2. Skid control ECU
C1256/57
 143
  1. Any of the wheel cylinder pressure sensor value is lower than the target value for at least 0.5 sec. when accumulator pressure is less than 14.62 MPa and vehicle speed is input.
  2. Accumulator pressure changes little when accumulator pressure is less than 14.62 MPa for at least 1 sec. without braking (pump motor is operating).
  3. Accumulator pressure is less than 14.62 MPa for at least 0.5 sec. when motor relay is malfunctioning.
  1. Brake actuator assembly (accumulator pressure, accumulator pressure sensor, pump motor)
  2. Skid control ECU

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 is 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. PROBLEM CHECK

  1. Ask the customer if frequent braking is performed when the ECB warning light comes on.

    Result:
    Condition
    		 Proceed To
    Frequent braking is performed
    		 A
    Frequent braking is not performed
    		 B

    HINT:
    This DTC is output even if the accumulator pressure drops only temporarily due to frequent braking.



 B
END
A


2. INSPECT BRAKE ACTUATOR ASSEMBLY

  1. F047491E01
    Disconnect the brake actuator assembly connector.

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

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



NG
REPLACE BRAKE ACTUATOR ASSEMBLY
OK


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

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch on.

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

    ABS / VSC / TRAC: 
    Item
    		 Measurement Item /
    Range (Display)
    		 Normal condition
    Accumulator Sensor
    		 Accumulator pressure sensor /
    min.: 0 V, max.: 5 V
    		 Specified value: 3.2 to 4.0 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

REPLACE SKID CONTROL ECU


← C1252/52C1259/58 →