DTC C1935: Ignition Switch Circuit

DTC detecting condition:  A fault is detected after a predetermined period of time, if the hardware IGN signal and CAN IGN signal were compared and did not match.

Trouble symptom: 

Brake warning light illuminates.

Wiring diagram: 

Vehicle stability control system Ref. to WIRING SYSTEM>VEHICLE STABILITY CONTROL SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK VSC (VDC) CONTROL MODULE & H/U INPUT VOLTAGE  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from the VSC (VDC) Control Module & H/U.
   3. Turn the ignition switch to ON.
   4. Measure the voltage between VSC (VDC) Control Module & H/U connector and chassis ground.

      Connector & terminal 

      (B66) No. 28 (+) - Chassis ground (-):

   Is the voltage 10 - 15 V?

   Yes:  Go to  2.

   No:  Repair or replace the open circuit in the power supply circuit including the fuse.

2. CHECK VSC (VDC) CONTROL MODULE & H/U GROUND CIRCUIT (CHECK FOR OPEN CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Measure the resistance between VSC (VDC) Control Module & H/U connector and chassis ground.

      Connector & terminal 

      (B66) No. 38 - Chassis ground:

   Is the resistance less than 10 Ω?

   Yes:  Go to  3.

   No:  Repair the VSC (VDC) Control Module & H/U ground circuit.

3. CHECK INPUT VOLTAGE OF BODY INTEGRATED UNIT  .

   Using the Subaru Select Monitor, read data of [IGN voltage] in the [Data Monitor] of [Body Control]. Ref. to BODY CONTROL (DIAGNOSTICS)>DATA MONITOR .

   Is the voltage 10 - 15 V?

   Yes:  Go to  4.

   No:  Perform the diagnosis for the body control system. Ref. to BODY CONTROL (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .

4. CHECK LAN SYSTEM  .

   Read the DTC of the LAN system using the Subaru Select Monitor. Ref. to LAN SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC for LAN system displayed?

   Yes:  Perform the diagnosis according to the DTC. Ref. to LAN SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST .

   No:  Go to  5.

5. CHECK POOR CONTACT OF CONNECTORS  .

   Is there poor contact of power supply circuit, ground circuit and VSC (VDC) Control Module & H/U connector?

   Yes:  Repair the connector.

   No:  Go to  6.

6. CHECK VSC (VDC) CONTROL MODULE & H/U  .
   1. Connect all connectors.
   2. Using the Subaru Select Monitor, perform the clear memory of [Brake Control]. Ref. to COMMON (DIAGNOSTICS)>CLEAR MEMORY .
   3. Execute the inspection mode. Ref. to BRAKE CONTROL (DIAGNOSTICS)>INSPECTION MODE .
   4. Read the DTC of [Brake Control] using the Subaru Select Monitor. Ref. to BRAKE CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is the same DTC displayed?

   Yes:  Replace the VSC (VDC) Control Module & H/U. Ref. to VEHICLE STABILITY CONTROL>VSC (VDC) CONTROL MODULE AND HYDRAULIC CONTROL UNIT (VSCCM & H/U) .

   No:  Go to  7.

7. CHECK DETECTION OF OTHER DTCS FOR VSC (VDC)  .

   Read the DTC of [Brake Control] using the Subaru Select Monitor. Ref. to BRAKE CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is any other DTC displayed?

   Yes:  Perform the diagnosis according to the DTC. Ref. to BRAKE CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST 

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