DTC C1957: LH Actuator Circuit

DTC detecting condition: 

• A fault is detected, if the motor control mismatch occurs during the motor operation.
• A fault is detected if the motor circuit or harness is open or shorted.

Trouble symptom: 

Parking brake system does not operate.

Failure detection pattern: 

• "Primary" (high-priority diagnosis)

Warning light/indicator light: 

The combination of DTC and warning light display may differ from the list depending on vehicle conditions and driving conditions at the time of failure detection.

• ABS warning light -
• VDC warning light & VDC operation indicator light -
• Electronic parking brake warning light (red)◦
• Brake warning light (EBD warning light) (red) -

Wiring diagram: 

Parking brake/brake fluid level warning light system Ref. to WIRING SYSTEM>PARKING BRAKE/BRAKE FLUID LEVEL WARNING LIGHT SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK HARNESS (CHECK FOR OPEN CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connectors from the VDCCM & H/U and rear brake caliper LH.
   3. Measure the resistance between VDCCM & H/U and rear brake caliper LH connector.

      Connector & terminal 

      (B66) No. 13 - (L142) No. 2:

      (B66) No. 12 - (L142) No. 1:

   Is the resistance less than 1 Ω?

   Yes:  GO TO  2.

   No:  Repair harness and connector between VDCCM & H/U and rear brake caliper LH connector.

2. CHECK HARNESS (CHECK FOR GROUND SHORT CIRCUIT)  .

   Measure the resistance between the rear brake caliper LH connector and chassis ground.

   Connector & terminal 

   (L142) No. 1 - Chassis ground:

   (L142) No. 2 - Chassis ground:

   Is the resistance 1 MΩ or more?

   Yes:  GO TO  3.

   No:  Repair ground short of harness between VDCCM & H/U and rear brake caliper LH connector.

3. CHECK HARNESS (CHECK FOR SHORT CIRCUIT TO POWER SUPPLY)  .
   1. Turn the ignition switch to ON.
   2. Measure the voltage between the rear brake caliper LH connector and chassis ground.

      Connector & terminal 

      (L142) No. 1 (+) - Chassis ground (-):

      (L142) No. 2 (+) - Chassis ground (-):

   Is the voltage less than 1 V?

   Yes:  GO TO  4.

   No:  Repair short to power supply of harness between VDCCM & H/U and rear brake caliper LH connector.

4. CHECK POOR CONTACT OF CONNECTORS  .

   Is there poor contact of power supply circuit, ground circuit and VDCCM & H/U connector?

   Yes:  Repair the connector.

   No:  GO TO  5.

5. CHECK REAR BRAKE CALIPER  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connectors from rear brake caliper LH.
   3. Measure the resistance between rear brake caliper LH terminals.

      Terminals 

      No. 1 - No. 2:

   Is the resistance less than 100 Ω?

   Yes:  Replace the VDCCM & H/U. Ref. to VEHICLE DYNAMICS CONTROL (VDC)>VDC CONTROL MODULE AND HYDRAULIC CONTROL UNIT (VDCCM & H/U) .

   No:  Replace the parking brake actuator assembly LH. Ref. to PARKING BRAKE>PARKING BRAKE ACTUATOR .