DTC C1521 Motor Relay: Wiring diagram

Vehicle dynamics control system Ref. to WIRING SYSTEM>Vehicle Dynamics Control System .

Fig 1: VDC System Wiring Diagram (Motor Relay)

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK VDCCM&H/U INPUT VOLTAGE. 
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from the VDCCM&H/U.
   3. Turn the ignition switch to ON.
   4. Measure the voltage between VDCCM&H/U connector and chassis ground.

      Connector & terminal 

      (B310) No. 4 (+) - Chassis ground (-):

      (B310) No. 26 (+) - Chassis ground (-):

   Is the voltage 10 - 15 V?

   • Yes  : Go to 2. 
   • No  : Repair the VDCCM&H/U power supply circuit.
2. CHECK VDCCM&H/U INPUT VOLTAGE. 

   Calculate the voltage difference measured in step 1.

   1. (B310) No. 4 (+) - Chassis ground (-):
   2. (B310) No. 26 (+) - Chassis ground (-):

   Is the voltage difference between A and B 2 V or more?

   • Yes  : Repair the power supply circuit.
   • No  : Go to 3. 
3. CHECK INSTALLATION OF VDCCM&H/U GROUND. 

   Is the VDCCM&H/U ground terminal installation bolt (ground bolt fixing onto the side frame upper face) installed correctly?

   • Yes  : Go to 4. 
   • No  : Install the VDCCM&H/U ground terminal installation bolt correctly.
4. CHECK VDCCM&H/U GROUND CIRCUIT (CHECK FOR OPEN CIRCUIT). 
   1. Turn the ignition switch to OFF.
   2. Measure the resistance between VDCCM&H/U connector and chassis ground.

      Connector & terminal 

      (B310) No. 14 - Chassis ground:

      (B310) No. 38 - Chassis ground:

   Is the resistance less than 10 Ω?

   • Yes  : Go to 5. 
   • No  : Repair the VDCCM&H/U ground harness.
5. CHECK VDCCM&H/U MOTOR RELAY. 

   Measure the resistance between VDCCM&H/U terminals.

   Terminals 

   No. 26 -No. 38:

   Is the resistance 1 MΩ or more?

   • Yes  : Go to 6. 
   • No  : Replace the VDCCM&H/U. Ref. to VEHICLE DYNAMICS CONTROL (VDC)>VDC Control Module and Hydraulic Control Unit (VDCCM&H/U) .
6. CHECK POOR CONTACT OF CONNECTORS. 

   Turn the ignition switch to OFF.

   Is there poor contact of connector between generator, battery and VDCCM&H/U?

   • Yes  : Repair the connector.
   • No  : Go to 7. 
7. CHECK VDCCM&H/U. 
   1. Connect all connectors.
   2. Clear the memory. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Clear memory .
   3. Perform the Inspection Mode. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Inspection Mode .
   4. Read the DTC. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) .

   Is the same DTC displayed?

   • Yes  : Replace the VDCCM&H/U. Ref. to VEHICLE DYNAMICS CONTROL (VDC)>VDC Control Module and Hydraulic Control Unit (VDCCM&H/U) .
   • No  : Go to 8. 
8. 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.