Symptom 6: Auto A/C, Navigation System Or Audio Does Not Operate

Probable defective cause: 

• Open circuit or short circuit to ground of DC/DC converter 1 power supply circuit
• Open circuit or short circuit to ground in harness between DC/DC converter 1 and fuse holder
• Open circuit or short circuit to ground in harness between fuse holder and each electrical part
• Blown out of fuse
• Poor contact of DC/DC converter 1 connector
• Faulty DC/DC converter 1

Wiring diagram: 

Auto Start Stop Ref. to WIRING SYSTEM>AUTO START STOP .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK FUSE  .

   Check the fuse located on the circuit of (B12) No. 5.

   Is the fuse blown out?

   Yes:  Check the following item and repair or replace if necessary.

   • Short circuit to ground in harness between fuse holder and each electrical part
   • Blown out of fuse

   No:  Go to  2 .

2. CHECK INPUT VOLTAGE OF DC/DC CONVERTER 1  .
   1. Turn the ignition switch to ON.
   2. Measure the voltage between DC/DC converter 1 and chassis ground.

      Connector and terminal 

      (B12) No. 5 (+) - Chassis ground (-):

   Is the voltage 10 V or more?

   Yes:  Go to  3 .

   No:  Check the following item and repair or replace if necessary.

   • Open or short to ground in harness of power supply circuit
   • Blown out of fuse
   • Short circuit to ground in harness between DC/DC converter 1 and fuse holder yes no
3. CHECK OUTPUT VOLTAGE OF DC/DC CONVERTER 1  .

   Measure the voltage between DC/DC converter 1 and chassis ground.

   Connector and terminal 

   (B11) No. 14 (+) - Chassis ground (-):

   (B11) No. 7 (+) - Chassis ground (-):

   (B11) No. 8 (+) - Chassis ground (-):

   Is the voltage 10 V or more?

   Yes:  Go to  4 .

   No:  Check for the poor contact of DC/DC converter 1 connector. Replace the DC/DC converter 1 if no fault is found. Ref. to STARTING/CHARGING SYSTEMS (H4DO)>AUTO START STOP DC/DC CONVERTER . Ref. to STARTING/CHARGING SYSTEMS (H4DOTC)>AUTO START STOP DC/DC CONVERTER .

4. CHECK HARNESS BETWEEN DC/DC CONVERTER 1 AND FUSE HOLDER  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the DC/DC converter 1 connector.
   3. Measure the resistance in harness between DC/DC converter 1 connector and fuse holder.

      Connector and terminal 

      (B11) No. 14 - Fuse holder:

      (B11) No. 7 - Fuse holder:

      (B11) No. 8 - Fuse holder:

   Is the resistance less than 1 Ω?

   Yes:  Repair the open circuit of harness between fuse holder and each electrical part. If the malfunction is not solved, perform the diagnosis for each electrical part.

   No:  Repair the open circuit of harness between DC/DC converter 1 and fuse holder.