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Check Brake Booster Assembly (With Master Cylinder)

  1. Perform the accumulator down drive. Ref. to BRAKE>BRAKE SYSTEM>OPERATION>ACCUMULATOR DOWN DRIVE .
  2. Check that the voltage of the 12 volt auxiliary battery is correct.
  3. Connect a measuring device as shown in the figure.
    G13935415Courtesy of SUBARU OF AMERICA, INC.
  4. Using the Subaru Select Monitor, perform the clear memory. Ref. to COMMON (DIAG)>CLEAR MEMORY .
  5. After bleeding air from the pressure gauge, perform the check.
  6. Perform the check for lack of boost action.
    1. Check and adjust the brake pedal. Ref. to BRAKE>BRAKE PEDAL>INSPECTION>BRAKE PEDAL .
    2. Check that the amount of brake fluid is between the lines of "MIN" and "MAX".
      G13935416Courtesy of SUBARU OF AMERICA, INC.
    3. Using the Subaru Select Monitor, select [Prohibiting Motor Control] on the [Work Support] display. Ref. to ELECTRIC BRAKE BOOSTER (DIAGNOSTICS)>WORK SUPPORT .
    4. Follow the instructions on the Subaru Select Monitor screen and prohibit motor control.
    5. Depress the brake pedal 40 times or more and return all brake fluid in the brake accumulator assembly to the reservoir tank.
      NOTE: There is a case that the buzzer may sound due to the lowering of accumulator pressure, but it is not abnormal.
    6. Check that the brake pedal does not stroke.
    7. Using the Subaru Select Monitor, read [Stroke Sensor 1 Revision Voltage] and [Stroke Sensor 2 Revision Voltage] on the [Data Monitor] display.
    8. Check the fluid pressure and each stroke sensor output value when the brake pedal is depressed.

    Specification: 

    Brake pedal force: N (kgf, lbf) 200 (20.4, 45) 500 (51, 112.4)
    Fluid pressure: kPa (kgf/cm2 , psi) 210 - 2210 (2.1 - 22.5, 30.4 - 320.4) 2460 - 4460 (25.1 - 45.5, 356.7 - 646.7)
    Stroke sensor 1 correction voltage: V 1.01 - 1.71 1.05 - 1.75
    Stroke sensor 2 correction voltage: V 3.29 - 3.99 3.25 - 3.95
    NOTE: Check the brake booster assembly (with master cylinder) by referring to the brake pedal operation force, fluid pressure and each stroke sensor output value. If there is a malfunction, check whether the brake booster assembly (with master cylinder) is normal or not by referring to each stroke sensor check result.
  7. Remove the pedal force gauge and pressure gauge, and bleed air from the brake line. Ref. to BRAKE>AIR BLEEDING>PROCEDURE>BRAKE LINE (HYBRID MODEL) .
  8. Using the Subaru Select Monitor, read [Accumulator Pressure] on the data monitor.

    Specification: 

    15, 000 - 21, 000 kPa (153 - 214.1 kgf/cm2 , 2, 175 - 3, 045 psi)

  9. Using the Subaru Select Monitor, perform the clear memory. Ref. to COMMON (DIAG)>CLEAR MEMORY .
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