DTC C1531: BLS Off Stuck

DTC Detecting condition: 

A fault is detected if stop light switch signal is OFF for a predetermined time or more with the pressure signal of the pressure sensor high.

Trouble symptom: 

• ABS does not operate.
• VDC does not operate.
• AVH does not function.
• EyeSight does not operate. (Models with EyeSight)

Wiring diagram: 

Stop light system Ref. to WIRING SYSTEM>STOP LIGHT SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK INSTALLATION POSITION OF STOP LIGHT SWITCH. 

   Check the installation position of the stop light switch. Ref. to BRAKE>STOP LIGHT SWITCH>INSPECTION>INSPECT THE SPECIFIED POSITION .

   Is the check result OK?

   Yes:  Go to  2.

   No:  Adjust the installation position of the stop light switch. Ref. to BRAKE>STOP LIGHT SWITCH>INSTALLATION .

2. CHECK STOP LIGHT SWITCH UNIT. 

   Perform the inspection of stop light switch unit. Ref. to BRAKE>STOP LIGHT SWITCH>INSPECTION>CHECK OUTPUT .

   Is the check result OK?

   Yes:  Go to  3.

   No:  Replace the stop light switch. Ref. to BRAKE>STOP LIGHT SWITCH .

3. CHECK STOP LIGHT RELAY. 

   Measure the resistance of stop light relay terminals.

   Terminals 

   No. 7 - No. 10:

   Is the resistance less than 1 Ω?

   Yes:  Go to  4.

   No:  Replace the stop light relay. Ref. to VEHICLE DYNAMICS CONTROL (VDC)>RELAY AND FUSE .

4. CHECK VDC Control Module & H/U CONNECTOR. 

   Disconnect the connector from the VDC Control Module & H/U.

   Is there poor contact or damage of the VDC Control Module & H/U connector?

   Yes:  Repair the VDC Control Module & H/U connector.

   No:  Go to  5.

5. CHECK STOP LIGHT SWITCH CIRCUIT (CHECK FOR OPEN CIRCUIT). 

   Measure the resistance of stop light switch circuit.

   Connector & terminal 

   (B310) No. 38 - (B225) No. 10:

   (B65) No. 2 - (B225) No. 7:

   (B65) No. 1 - (F/B fuse) No. 37:

   Is the resistance less than 1 Ω?

   Yes:  Go to  6.

   No:  Repair the stop light switch circuit.

6. CHECK STOP LIGHT SWITCH CIRCUIT. 
   1. Connect all connectors.
   2. Turn the ignition switch to ON.
   3. Measure the voltage between stop light relay and chassis ground.

      Connector & terminal 

      (B225) No. 10 (+) - Chassis ground (-):

      Is the voltage 10 V or more when the stop light switch is ON (when pedal is depressed)?

      Yes:  Go to  7.

      No:  Repair the stop light switch circuit.

7. CHECK VDC Control Module & H/U. 
   1. Using the Subaru Select Monitor, perform the clear memory. Ref. to COMMON (DIAG)>CLEAR MEMORY .
   2. Execute the inspection mode. Ref. to BRAKE CONTROL (DIAGNOSTICS)>INSPECTION MODE .
   3. Read the DTC using Subaru Select Monitor. Ref. to BRAKE CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

      Is the same DTC displayed?

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

      No:  Go to  8.

8. CHECK DETECTION OF OTHER DTCS FOR VDC. 

   Read the DTC using 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.