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: 

• AVH does not function. (Models with EyeSight)
• Parking brake system does not operate.
  NOTE: This DTC may be stored when the rear brake caliper connector is disconnected regardless of the ignition switch condition (ON/OFF). Perform the Clear Memory Mode after diagnosis if a DTC is recorded. Refer to VEHICLE DYNAMICS CONTROL (VDC) (DIAGNOSTICS)>CLEAR MEMORY MODE .

Wiring diagram: 

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

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 VDC Control Module & H/U and rear brake caliper LH.
   3. Measure the resistance between VDC Control Module & H/U and rear brake caliper LH connector.

      Connector & terminal 

      (B310) No. 12 - (R154) No. 1:

      (B310) No. 13 - (R154) No. 2:

   Is the resistance less than 1 Ω?

   Yes:  Go to  2.

   No:  Repair harness and connector between VDC Control Module & 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 

   (R154) No. 1 - Chassis ground:

   (R154) No. 2 - Chassis ground:

   Is the resistance 1 MΩ or more?

   Yes:  Go to  3.

   No:  Repair ground short of harness between VDC Control Module & 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 

      (R154) No. 1 (+) - Chassis ground (-):

      (R154) No. 2 (+) - Chassis ground (-):

   Is the voltage less than 2 V?

   Yes:  Go to  4.

   No:  Repair short to power supply of harness between VDC Control Module & 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 VDC Control Module & 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 VDC Control Module & H/U. Refer to VEHICLE DYNAMICS CONTROL (VDC)>VDC CONTROL MODULE AND HYDRAULIC CONTROL UNIT (VDCCM & H/U) .

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