ELECTRONICALLY CONTROLLED BRAKE SYSTEM(w/o Vacuum Brake Booster), 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 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 591

Either of the following is detected:


  1. Accumulator pressure sensor input does not increase before braking and while the pump motor is operating.

  2. Accumulator pressure sensor input reduction rate exceeds the specification before braking and while the pump motor is not operating.

  • Brake fluid leaks

  • Brake booster with accumulator pump assembly

  • Brake actuator assembly

 -
DTC Detection Conditions: C1391 INF Code: 591
Vehicle Condition
Pattern 1 Pattern 2
Diagnosis Condition Before braking and while the pump motor is operating ○ -
Before braking and while the pump motor is not operating - ○
Malfunction Status The accumulator pressure sensor input does not rise ○ -
The proportional drop in the accumulator pressure sensor input exceeds the standard value - ○
Detection Time - -
Number of Trips 1 trip 1 trip

CAUTION / NOTICE / HINT

Note

When replacing the brake actuator assembly, perform initialization and calibration of the linear solenoid valve.

Click here

PROCEDURE


  1. RECONFIRM DTC


    1. Start the engine.

    2. Check if the same DTC is output.

      Click here


      Chassis > ABS/VSC/TRC > Trouble Codes
      Result
      Result Proceed to
      DTC C1365 is output. A
      DTC C1365 is not output. B

    B

    GO TO DTC (C1365) Click here

    A

  2. CHECK FOR FLUID LEAK


    1. Check that there are no fluid leaks in the brake lines between the brake booster with accumulator pump assembly and the brake actuator assembly.

    2. Check that there are no fluid leaks in the brake lines between the brake actuator assembly and the wheel cylinders.

    3. Check that the brakes are not dragging.

      OK
      There are no fluid leaks or dragging.
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE APPLICABLE PART

    OK

  3. READ VALUE USING GTS (ACCUMULATOR PRESSURE SENSOR)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Select the Data List on the GTS.

      Click here


      Chassis > ABS/VSC/TRC > Data List
      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      Accumulator Sensor Accumulator pressure sensor Min.: 0.00 V, Max.: 5.00 V Specified value: 2.60 to 3.80 V 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
      Accumulator Sensor

    4. Depress the brake pedal 4 or 5 times and operate the pump motor.

    5. Wait for 30 seconds without depressing the brake pedal.

    6. Check that the accumulator pressure sensor output value change is within the specified range.

      OK
      Accumulator pressure sensor output value change is less than 0.20 V.

      Tech Tips


      • This inspection is performed to determine if a long-term power malfunction occurred when low pressure is detected due to a defective sensor, an internal leak in the brake actuator assembly, or deterioration of the accumulator.

      • External brake fluid leaks are suspected if the fluid level drops inside the brake master cylinder reservoir assembly.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE BRAKE BOOSTER WITH ACCUMULATOR PUMP ASSEMBLY Click here

    NG

  4. PERFORM ACTIVE TEST USING GTS (SOLENOID VALVE)


    1. With the brake pedal released, set "ECB Solenoid (SMC1)" to "ON" and check the output voltage of "FR W/C Sensor".

      ECB: Electronically Controlled Brake System

      Click here


      Chassis > ABS/VSC/TRC > Active Test
      Tester Display Measurement Item Control Range Diagnostic Note
      ECB Solenoid (SMC1) Master cut solenoid (SMC1) Solenoid ON/OFF ECB: Electronically Controlled Brake System

      Chassis > ABS/VSC/TRC > Data List
      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      FR W/C Sensor Front wheel cylinder pressure sensor RH Min.: 0.00 V, Max.: 5.00 V Brake pedal released: 0.30 to 0.70 V Reading increases when brake pedal is depressed

      Chassis > ABS/VSC/TRC > Active Test
      Active Test Display
      ECB Solenoid (SMC1)
      Data List Display
      FR W/C Sensor

      ECB: Electronically Controlled Brake System

      OK
      The output value of the wheel cylinder pressure sensor does not increase.

      Tech Tips

      If output value increases, there may be brake fluid leaks in the brake actuator assembly.

      Result
      Result Proceed to
      The output values of the wheel cylinder pressure sensors do not increase. A
      The output value of the wheel cylinder pressure sensor increases. B

    B

    GO TO STEP 8 Click here

    A

  5. PERFORM ACTIVE TEST USING GTS (SOLENOID VALVE)


    1. With the brake pedal released, set "ECB Solenoid (SMC2)" to "ON" and check the output voltage of "FL W/C Sensor".

      ECB: Electronically Controlled Brake System

      Click here


      Chassis > ABS/VSC/TRC > Active Test
      Tester Display Measurement Item Control Range Diagnostic Note
      ECB Solenoid (SMC2) Master cut solenoid (SMC2) Solenoid ON/OFF ECB: Electronically Controlled Brake System

      Chassis > ABS/VSC/TRC > Data List
      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      FL W/C Sensor Front wheel cylinder pressure sensor LH Min.: 0.00 V, Max.: 5.00 V Brake pedal released: 0.30 to 0.70 V Reading increases when brake pedal is depressed

      Chassis > ABS/VSC/TRC > Active Test
      Active Test Display
      ECB Solenoid (SMC2)
      Data List Display
      FL W/C Sensor

      ECB: Electronically Controlled Brake System

      OK
      The output value of the wheel cylinder pressure sensor does not increase.

      Tech Tips

      If output value increases, there may be brake fluid leaks in the brake actuator assembly.

      Result
      Result Proceed to
      The output values of the wheel cylinder pressure sensors do not increase. A
      The output value of the wheel cylinder pressure sensor increases. B

    B

    GO TO STEP 8 Click here

    A

  6. PERFORM ACTIVE TEST USING GTS (SOLENOID VALVE)


    1. With the brake pedal released, set the current of "ECB Solenoid (SLRRR)" to 1.2 A and check the output voltage of "RR W/C Sensor".

      ECB: Electronically Controlled Brake System

      Click here


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

      Chassis > ABS/VSC/TRC > Data List
      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      RR W/C Sensor Rear wheel cylinder pressure sensor RH Min.: 0.00 V, Max.: 5.00 V Brake pedal released: 0.30 to 0.70 V Reading increases when brake pedal is depressed

      Chassis > ABS/VSC/TRC > Active Test
      Active Test Display
      ECB Solenoid (SLRRR)
      Data List Display
      RR W/C Sensor

      ECB: Electronically Controlled Brake System

      OK
      The output value of the wheel cylinder pressure sensor does not increase.

      Tech Tips

      If output value increases, there may be brake fluid leaks in the brake actuator assembly.

      Result
      Result Proceed to
      The output values of the wheel cylinder pressure sensors do not increase. A
      The output value of the wheel cylinder pressure sensor increases. B

    B

    GO TO STEP 8 Click here

    A

  7. PERFORM ACTIVE TEST USING GTS (SOLENOID VALVE)


    1. With the brake pedal released, set the current of "ECB Solenoid (SLRRL)" to 1.2 A and check the output voltage of "RL W/C Sensor".

      ECB: Electronically Controlled Brake System

      Click here


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

      Chassis > ABS/VSC/TRC > Data List
      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      RL W/C Sensor Rear wheel cylinder pressure sensor LH Min.: 0.00 V, Max.: 5.00 V Brake pedal released: 0.30 to 0.70 V Reading increases when brake pedal is depressed

      Chassis > ABS/VSC/TRC > Active Test
      Active Test Display
      ECB Solenoid (SLRRL)
      Data List Display
      RL W/C Sensor

      ECB: Electronically Controlled Brake System

      OK
      The output value of the wheel cylinder pressure sensor does not increase.

      Tech Tips

      If output value increases, there may be brake fluid leaks in the brake actuator assembly.

      Result
      Result Proceed to
      The output values of the wheel cylinder pressure sensors do not increase. A
      The output value of the wheel cylinder pressure sensor increases. B

    A

    REPLACE BRAKE BOOSTER WITH ACCUMULATOR PUMP ASSEMBLY Click here

    B

  8. REPLACE BRAKE ACTUATOR ASSEMBLY


    1. Replace the brake actuator assembly.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    REPLACE BRAKE BOOSTER WITH ACCUMULATOR PUMP ASSEMBLY Click here The load on the brake booster pump with accumulator assembly is increased due to fluid leaking inside the brake actuator assembly. The performance of the brake booster pump with accumulator assembly may decrease. Therefore, replace the brake booster pump with accumulator assembly at the same time.