DTC C1521: Motor Relay

DTC detecting condition: 

A fault is detected if the pump motor supply voltage becomes significantly low when the pump motor is not driven.

Trouble symptom: 

• ABS does not operate sometimes.
• VDC does not operate.
• AVH does not function.
• EyeSight does not operate.

Failure detection pattern: 

• "Primary" (high-priority diagnosis)

Warning light/indicator light: 

The combination of DTC and warning light display may differ from the list depending on vehicle conditions and driving conditions at the time of failure detection.

• ABS warning light◦
• VDC warning light & VDC operation indicator light◦
• Electronic parking brake warning light (red)◦
• Brake warning light (EBD warning light) (red)◦

Wiring diagram: 

Vehicle dynamics control system Ref. to WIRING SYSTEM>VEHICLE DYNAMICS CONTROL SYSTEM>WIRING DIAGRAM .

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 

      (B66) No. 1 (+) - Chassis ground (-):

      (B66) No. 36 (+) - 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. (B66) No. 1 (+) - Chassis ground (-):
   2. (B66) No. 36 (+) - 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 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 

      (B66) No. 14 - 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. 1 - No. 14:

   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. 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 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  .

   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.