DTC C1572 Brake Lamp Relay On Stuck: Wiring diagram

Stop light system Ref. to WIRING SYSTEM>Stop Light System>WIRING DIAGRAM>EXCEPT FOR MODEL WITHOUT EyeSight AND X MODE .

Fig 1: Stop Light System Wiring Diagram (Brake Lamp Relay ON Stuck)

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK FUSE. 
   1. Turn the ignition switch to OFF.
   2. Check the fuse (No. 33).

   Is the fuse blown out?

   • Yes  : Replace the fuse (No. 33).
   • No  : Go to 2. 
2. CHECK STOP LIGHT RELAY. 

   Measure the resistance between brake light relay terminals.

   Terminals 

   No. 14 -No. 16:

   Is the resistance less than 1 Ω?

   • Yes  : Go to 3. 
   • No  : Replace the stop light relay.
3. CHECK VDCCM&H/U CONNECTOR. 

   Disconnect the connector from the VDCCM&H/U.

   Is there poor contact or damage of the VDCCM&H/U connector?

   • Yes  : Repair the VDCCM&H/U connector.
   • No  : Go to 4. 
4. CHECK STOP LIGHT RELAY CIRCUIT. 

   Measure the resistance between the stop light relay and the fuse or the VDCCM&H/U connector.

   Connector & terminal 

   (B564) No. 14 - (B310) No. 28:

   (B564) No. 16 - (F/B fuse) No. 33:

   Is the resistance less than 1 Ω?

   • Yes  : Go to  5.
   • No  : Repair the stop light relay circuit.
5. CHECK STOP LIGHT RELAY 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 

      (B564) No. 16 (+) - Chassis ground (-):

   Is the voltage 10 V or more?

   • Yes  : Go to 6. 
   • No  : Repair the stop light relay circuit.
6. CHECK VDCCM&H/U. 
   1. Clear the memory. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Clear memory .
   2. Read the DTC. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) .

   Is the same DTC displayed?

   • Yes  : Replace the VDCCM only. Ref. to VEHICLE DYNAMICS CONTROL (VDC)>VDC Control Module and Hydraulic Control Unit (VDCCM&H/U)>REPLACEMENT .
   • No  : Go to 7. 
7. CHECK DETECTION OF OTHER DTCS FOR VDC. 

   Ref. to BRAKE CONTROL (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) .

   Is any other DTC displayed?

   • Yes  : Perform the diagnosis according to DTC. Ref. to BRAKE CONTROL (DIAGNOSTICS)>List of Diagnostic Trouble Code (DTC) .
   • No  : Currently, it is normal. There may have been a temporary poor contact in the harness and connector or a temporary noise interference.