ELECTRONICALLY CONTROLLED BRAKE SYSTEM, Diagnostic DTC:C120F

DTC Code DTC Name
C120F Open in Master Reservoir Level Switch Circuit

DESCRIPTION

If the skid control ECU (brake booster with master cylinder assembly) detects that the brake fluid level is low or there is an open in the brake fluid level warning switch signal circuit, DTC C120F is stored.

DTC No. Detection Item INF Code DTC Detection Condition Trouble Area Note
C120F Open in Master Reservoir Level Switch Circuit 371 The brake fluid level warning switch (brake booster with master cylinder assembly) circuit is open for 2 seconds or more.

  • Open in brake fluid level warning switch (brake booster with master cylinder assembly)

  • Open in wire harness

  • Skid control ECU (brake booster with master cylinder assembly)

 Electronically controlled brake system DTC

WIRING DIAGRAM

Refer to DTC C1202.

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CAUTION / NOTICE / HINT

Note

After replacing the skid control ECU (brake booster with master cylinder assembly), perform linear solenoid valve offset learning, ABS holding solenoid valve learning, yaw rate and acceleration sensor zero point calibration and system information memorization after performing "Reset Memory".

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PROCEDURE


  1. CHECK BRAKE FLUID LEVEL


    1. Check that the brake fluid level is sufficient.

      Tech Tips

      If the fluid level is low, check for fluid leaks, and repair as necessary.


      1. Check for brake fluid leaks (connection between the brake booster pump assembly, brake actuator assembly, brake booster with master cylinder assembly and wheel cylinders).

        Tech Tips

        If no leaks exist, add and adjust fluid using the GTS.

        Click here

      2. Check that the DTC is not output again.

        Click here


        Chassis > ABS/VSC/TRC > Trouble Codes

    2. Check that there are no leaks from the connections between the brake booster pump assembly, brake actuator assembly and brake booster with master cylinder assembly.

      Tech Tips

      As a visual check is very difficult, perform the check with the following procedure.


      1. Bleed the air from the brake system.

        Click here

      2. Turn the power switch off.

      3. Disconnect the A44 brake pedal stroke sensor assembly connector.

      4. Select the Data List on the GTS.

        Click here


        Chassis > ABS/VSC/TRC > Data List
        Tester Display Measurement Item Range Normal Condition Diagnostic Note
        MT Voltage Value MT voltage value Min.: 0.00 V, Max.: 20.00 V

        Pump motor off: 0.00 V

        Pump motor on: 12.00 V

        		 -
        Accumulator Pressure Accumulator pressure output value Min.: 0.00 MPa, Max.: 24.48 MPa

        15.00 to 21.00 MPa

        (Pressure stable and pump motor stopped)

        		 When brake fluid is stored in the accumulator: Accumulator pressure changes in accordance with volume of fluid stored in the accumulator

        Chassis > ABS/VSC/TRC > Data List
        Tester Display
        MT Voltage Value
        Accumulator Pressure

      5. Depress the brake pedal several times to operate the pump motor, then wait until it stops.

      6. After the pump motor stops, wait for 30 seconds, then check the drop in the accumulator pressure sensor output value and the state of the pump motor.

      Result
      Result Proceed to
      The drop in the accumulator pressure sensor output value is less than 2.50 MPa 30 seconds after the pump motor stops, and the pump motor does not operate within 30 seconds after the pump motor stops. A
      The drop in the accumulator pressure sensor output value is 2.50 MPa or more 30 seconds after the pump motor stops, or the pump motor operates within 30 seconds after the pump motor stops. B

    B

    CHECK AND REPAIR BRAKE FLUID LEAKS OR ADD FLUID

    A

  2. INSPECT BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY (BRAKE FLUID LEVEL WARNING SWITCH)


    1. A001P3HC19
      *a

      Component without harness connected

      (Brake Fluid Level Warning Switch (Brake Booster with Master Cylinder Assembly))

      Turn the power switch off.

    2. Reconnect the A44 brake pedal stroke sensor assembly connector.

    3. Remove the brake master cylinder reservoir filler cap assembly.

    4. Make sure that there is no looseness at the locking part and the connecting part of the connector.

      OK
      The connector is securely connected.

    5. Disconnect the A43 brake fluid level warning switch (brake booster with master cylinder assembly) connector.

    6. Check both the connector case and the terminals for deformation and corrosion.

      OK
      No deformation or corrosion.

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

      Tech Tips

      A float is located inside the brake master cylinder reservoir assembly (brake booster with master cylinder assembly). Its position changes according to the level of brake fluid.

      Standard Resistance
      Tester Connection Condition Specified Condition
      2 (LBL) - 1 (GND) Brake fluid level warning switch (brake booster with master cylinder assembly) off (float up) 1.84 to 2.16 kΩ
      2 (LBL) - 1 (GND) Brake fluid level warning switch (brake booster with master cylinder assembly) on (float down)

      Below 1 Ω

      (Brake fluid level is low)

      Tech Tips

      If there are no problems after completing the preceding inspection, adjust the brake fluid to the MAX level with the power switch on (IG).

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

    B

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY Click here

    C

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY Click here

    A

  3. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - BRAKE FLUID LEVEL WARNING SWITCH (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY))


    1. Turn the power switch off.

    2. Make sure that there is no looseness at the locking part and the connecting part of the connector.

      OK
      The connector is securely connected.

    3. Disconnect the A39 skid control ECU (brake booster with master cylinder assembly) connector.

    4. Check both the connector case and the terminals for deformation and corrosion.

      OK
      No deformation or corrosion.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A39-16 (LBL) - A43-2 (LBL) Always Below 1 Ω
      A39-16 (LBL) or A43-2 (LBL) - Body ground Always 10 kΩ or higher
      A43-1 (GND) - Body ground Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. CHECK BRAKE DISC


    1. Reconnect the A39 skid control ECU (brake booster with master cylinder assembly) connector.

    2. Reconnect the A43 brake fluid level warning switch (brake booster with master cylinder assembly) connector.

    3. Disconnect the A44 brake pedal stroke sensor assembly connector.

    4. Perform a road test according to Freeze Frame Data or customer problem analysis. While driving, check for abnormal brake pedal vibration caused by brake discs that are worn or have excess runout.

      OK
      Brake pedal does not vibrate during braking.

      Tech Tips


      • An unevenly worn disc may vibrate the caliper pistons and cause fluctuations in brake line pressure, triggering a malfunction detection condition.

      • The brake pedal does not kick back due to caliper piston vibration during electronically controlled brake system control.

      • If the brake pedal stroke sensor assembly connector is disconnected, the fail-safe function will prohibit electronically controlled brake system control.

      • The Active Test does not prohibit electronically controlled brake system control when the vehicle is being driven, so disconnect the brake pedal stroke sensor assembly connector before continuing with inspection.

      • Uneven disc wear can be checked by measuring the disc thickness variation.

        for Front Brake: Click here

        for Rear Brake: Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE BRAKE DISC

    OK

  5. RECONFIRM DTC


    1. Turn the power switch off.

    2. Reconnect the A44 brake pedal stroke sensor assembly connector.

    3. Clear the DTCs.

      Click here


      Chassis > ABS/VSC/TRC > Clear DTCs

    4. Turn the power switch off.

    5. Turn the power switch on (READY).

    6. Perform a road test.

    7. Check if the same DTC is output.

      Click here


      Chassis > ABS/VSC/TRC > Trouble Codes
      Result
      Result Proceed to
      DTC C120F is not output. A
      DTC C120F is output. (for LHD) B
      DTC C120F is output. (for RHD) C

    A

    USE SIMULATION METHOD TO CHECK Click here

    B

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY Click here

    C

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY Click here