ELECTRONICALLY CONTROLLED BRAKE SYSTEM, Diagnostic DTC:C1391

DTC Code DTC Name
C1391 Abnormal Leak in Accumulator

DESCRIPTION

This DTC is stored if internal or external brake fluid leaks are detected due to improper sealing in the brake actuator (brake booster with master cylinder assembly) or brake booster pump assembly. Internal leaks are suspected if the pump motor operates frequently without braking.

DTC No. Detection Item INF Code DTC Detection Condition Trouble Area Note
C1391 Abnormal Leak in Accumulator 351

Either of the following is detected:


  1. When the brake pedal is not depressed and the pump motor is operating, the accumulator pressure sensor value does not increase a certain number of times.

  2. When the brake pedal is not depressed and the pump motor is not operating, the accumulator pressure sensor decrease rate exceeds a certain threshold a certain number of times.

  • Brake fluid leaks

  • Brake actuator (brake booster with master cylinder assembly)

    (Malfunctioning internal seal etc.)

  • Brake booster pump assembly

    (Accumulator internal gas pressure decrease, etc.)

 Electronically controlled brake system DTC
DTC Detection Conditions: C1391 INF Code: 351
Vehicle Condition
Pattern 1 Pattern 2
Diagnosis Condition Brake pedal not depressed and pump motor operating. ○ -
Brake pedal not depressed and pump motor not operating. - ○
Malfunction Status The accumulator pressure sensor value does not increase a certain number of times. ○ -
The accumulator pressure sensor decrease rate exceeds a certain threshold a certain number of times. - ○
Detection Time - -
Number of Trips 1 trip 1 trip

Tech Tips

DTC will be output when conditions for either of the patterns in the table above are met.

CAUTION / NOTICE / HINT

Note

After replacing the brake actuator (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".

Click here

PROCEDURE


  1. READ VALUE USING GTS (SERVO PRESSURE)


    1. Select the Active Test on the GTS.

      Click here


      Chassis > ABS/VSC/TRC > Active Test
      Tester Display Measurement Item Control Range Diagnostic Note
      ECB Solenoid (SLR) Linear solenoid reduction valve (SLR) Solenoid ON/OFF ECB: Electronically Controlled Brake System

      Chassis > ABS/VSC/TRC > Active Test
      Tester Display
      ECB Solenoid (SLR)

    2. Select the Data List on the GTS.

      Click here


      Chassis > ABS/VSC/TRC > Data List
      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      Servo Pressure Pressure value of servo Min.: 0.00 MPa, Max.: 24.48 MPa Brake pedal released: 0.00 to 2.10 MPa Brake pedal is being depressed: Changes in proportion to the depression force of the brake pedal

      Chassis > ABS/VSC/TRC > Data List
      Tester Display
      Servo Pressure

    3. Perform the Active Test and operate the linear solenoid (SLR) in the brake actuator (brake booster with master cylinder assembly).

    4. Check that the servo pressure output value does not increase when performing the Active Test.

      OK
      The servo pressure output value does not increase when performing the Active Test.

      Tech Tips

      If the servo pressure output value increases, an internal brake fluid leak in the brake actuator (brake booster with master cylinder assembly) is suspected.

      Result
      Result Proceed to
      The servo pressure output value increases. A
      The servo pressure output value does not increase. B

    A

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY for LHD: Click here
    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY for RHD: Click here

    B

  2. CHECK OPERATING TIME OF PUMP MOTOR


    1. Turn the power switch on (READY).

    2. 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

      		 -

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

    3. With the power switch on (READY), check the operation of the pump motor.

      OK
      The pump motor operates once or more within 20 seconds or operates for 10 seconds or more each time.
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY for LHD: Click here
    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY for RHD: Click here

    OK

  3. CHECK FOR FLUID LEAK


    1. Check for brake fluid leaks in the line from the brake booster pump assembly to the brake booster with master cylinder assembly.

      Click here

      OK
      There are no brake fluid leaks.
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER PUMP ASSEMBLY for the brake booster with master cylinder assembly (for LHD): Click here
    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER PUMP ASSEMBLY for the brake booster with master cylinder assembly (for RHD): Click here
    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER PUMP ASSEMBLY for the brake booster pump assembly (for LHD): Click here
    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER PUMP ASSEMBLY for the brake booster pump assembly (for RHD): Click here

    NG

    MALFUNCTIONING PART