DTC C0594 Brake Booster Motor "A" Performance: Notes

1. - 

DTC detecting condition: 

• DTC C0594

  Pump motor drive status continues for 178 seconds or more (this would be 98 seconds more with faulty relay).

• DTC C1B5E (detail code: 321, 327, 328)

  Open circuit condition of motor relay drive circuit continues for 0.2 seconds or more.

• DTC C1B5F (detail code: 322)

  Short circuit condition of motor relay drive circuit continues for 2 seconds or more.

Trouble symptom: 

• Brake cannot be controlled. (Except when detail code 327/328 occurs.)
• Regenerative brake cannot be controlled. (Except when detail code 327/328 occurs.)
• Brake assist does not operate. (Except when detail code 327/328 occurs.)
• EyeSight functions (ACC/PCS) do not operate.

Wiring diagram: 

Electronic controlled brake system Ref. to WIRING SYSTEM (CROSSTREK MODEL (HEV))>ELECTRIC CONTROL BRAKE SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DATA MONITOR  .
   1. Turn to READY ON.
   2. Using the Subaru Select Monitor, display the following items in the [Data Monitor] of [Electric Brake Booster]. Ref. to ELECTRIC BRAKE BOOSTER (DIAGNOSTICS)>DATA MONITOR .
      • Motor Relay 1
      • Motor Relay 2
   3. Depress the brake pedal several times to check the operating condition.

   Do [Motor Relay 1] and [Motor Relay 2] turn to [ON]/[OFF]?

   Yes:  Go to  2.

   No:  Go to  8.

2. CHECK CONNECTOR  .

   Check the connecting condition of the brake accumulator assembly connector.

   Is there looseness, deformation, or corrosion at the connectors?

   Yes:  Repair or replace the connector.

   No:  Go to  3.

3. CHECK BRAKE ACCUMULATOR ASSEMBLY  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the brake accumulator assembly connector.
   3. Measure the resistance between terminals of brake accumulator assembly.

      Terminals 

      No. 1 - No. 3: (Resistance: 10 Ω or less)

      No. 2 - No. 4: (Resistance: 10 Ω or less)

      No. 1 - No. 2: (Resistance: Less than 1 Ω)

      No. 3 - No. 4: (Resistance: Less than 1 Ω)

   Does the resistance indicate the standard value?

   Yes:  Go to  4.

   No:  Replace the brake accumulator assembly. Ref. to BRAKE>BRAKE ACCUMULATOR ASSY .

4. CHECK HARNESS  .

   Measure the resistance between brake accumulator assembly connector and chassis ground.

   Connector & terminal 

   (B653) No. 3 - Chassis ground:

   (B653) No. 4 - Chassis ground:

   Is the resistance less than 1 Ω?

   Yes:  Go to  5.

   No:  Repair or replace the harness.

5. CHECK DATA MONITOR  .
   1. Connect the brake accumulator assembly connector.
   2. Disconnect the brake stroke sensor connector.
   3. Using Subaru Select Monitor, display [Accumulator Pressure] in [Data Monitor] of [Electric Brake Booster]. Ref. to ELECTRIC BRAKE BOOSTER (DIAGNOSTICS)>DATA MONITOR .
   4. Depress the brake pedal several times so that the pump motor operates, then wait until it stops.
   5. Wait for 30 seconds from the moment the pump motor stops, then check the amount of [Accumulator Pressure] drop and the condition of the pump motor.

   Is the amount of [Accumulator Pressure] drop after 30 seconds less than 2.50 MPa, and does the pump motor start operating within 30 seconds?

   Yes:  Go to  7.

   No:  Go to  6.

6. CHECK DTC  .
   1. Turn the ignition switch to OFF.
   2. Connect the brake stroke sensor connector.
   3. Using the Subaru Select Monitor, perform the clear memory of [Electric Brake Booster]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
   4. Read the DTC of [Electric Brake Booster] using the Subaru Select Monitor. Ref. to ELECTRIC BRAKE BOOSTER (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Are DTCs C0594, C1B5E, and C1B5F displayed?

   Yes:  Replace the brake booster assembly (with the master cylinder). Ref. to BRAKE>BRAKE BOOSTER .

   No:  Currently, it is normal. There may have been a temporary poor contact in the harness and connector or a temporary noise interference.

7. CHECK DATA MONITOR  .
   1. Turn the ignition switch to OFF.
   2. Connect the brake stroke sensor connector.
   3. Using Subaru Select Monitor, display [Servo Pressure] in [Data Monitor] of [Electric Brake Booster]. Ref. to ELECTRIC BRAKE BOOSTER (DIAGNOSTICS)>DATA MONITOR .
   4. Depress the brake pedal to the floor and check to see if the [Servo Pressure] changes in response to amount of brake pedal stroke.
      NOTE: [Servo Pressure] should not rise when the pedal is released.

   Does the [Servo Pressure] remain risen?

   Yes:  Replace the brake booster assembly (with the master cylinder). Ref. to BRAKE>BRAKE BOOSTER .

   No:  Replace the brake accumulator assembly. Ref. to BRAKE>BRAKE ACCUMULATOR ASSY .

8. CHECK CONNECTOR  .

   Check the connecting condition of EBB control module.

   Is there looseness, deformation, or corrosion at the connectors?

   Yes:  Repair or replace the connector.

   No:  Go to  9.

9. CHECK INTERMEDIATE CONNECTOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the coupling connector. (AD81, B652)
   3. Disconnect the brake accumulator assembly connector.
   4. Measure the voltage between intermediate connector and chassis ground.

      Connector & terminal 

      (B652) No. 21 (+) - Chassis ground (-):

      (B652) No. 24 (+) - Chassis ground (-):

   Is the voltage 11 - 14 V?

   Yes:  Go to  10.

   No:  Repair or replace the harness.

10. CHECK EBB CONTROL MODULE AND INTERMEDIATE CONNECTOR  .
    1. Disconnect the EBB control module connector.
    2. Measure the resistance between EBB control module connector and intermediate connector.

       Connector & terminal 

       (AD82) No. 1 - (AD81) No. 25:

       (AD82) No. 2 - (AD81) No. 21:

       (AD82) No. 3 - (AD81) No. 22:

       (AD82) No. 4 - (AD81) No. 24:

    Is the resistance less than 1 Ω?

    Yes:  Replace the brake booster assembly (with the master cylinder). Ref. to BRAKE>BRAKE BOOSTER .

    No:  Repair or replace the harness.