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Home › Toyota › 2007 › Prius Base › Repair and Diagnosis › Brakes › Brakes Control Systems › Brake Control System › Electronically Controlled Brake System › DTC C1256/57 Accumulator Low Pressure › Inspection Procedure

Inspection Procedure

NOTE: When replacing the skid control ECU, perform initialization of linear solenoid valve and calibration (see INITIALIZATION  ).

HINT:

DTCs may be output if the accumulator pressure drops due to frequent braking (this is not a malfunction).

  1. INSPECT BRAKE ACTUATOR ASSEMBLY 
    1. Disconnect the brake actuator connector.
    2. Measure the resistance of the actuator.

      Standard resistance 

      STANDARD RESISTANCE REFERENCE CHART

      Tester Connection Specified Condition
      A2-1 (BM2) - A2-31 (GND1) Below 10 Ω
      A2-2(BM1) - A2-31 (GND1) Below 10 Ω
      A2-1 (BM2) - A2-2(BM1) Below 1 Ω
      A2-31 (GND1) - A2-32 (GND2) Below 1 Ω
      A2-1 (BM2) - A2-33 (MTT) Approx. 10 Ω
      A2-2(BM1) - A2-33(MTT) Approx. 10 Ω

    NG: REPLACE BRAKE ACTUATOR ASSEMBLY 

    Fig 1: Inspecting Brake Actuator Assembly
    G05189268Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    OK: Go to Next Step 

  2. READ VALUE OF INTELLIGENT TESTER (ACCUMULATOR PRESSURE SENSOR) 
    1. Check the DATA LIST for proper functioning of the accumulator pressure sensor.
    2. 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).

      Skid control ECU 

      SKID CONTROL ECU DIAGNOSTIC CHART

      Item Measurement Item / Range (Display) Normal condition Diagnostic Note
      ACC PRESS SENS 1 Accumulator pressure sensor 1 / Min.: 0V, Max.: 5V Specified value: 3.2 to 4.0 V -

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

    NG: REPLACE BRAKE ACTUATOR ASSEMBLY 

    OK: REPLACE SKID CONTROL ECU 

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