DTC U0284: Lost Communication With Active Grille Shutter Module "A": Notes

DTC detecting condition: 

Immediately at fault recognition

Wiring diagram: 

Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .
   1. Turn the ignition switch to ON.
   2. Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. (Ref. to COMMON (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

      Is DTC U0284 displayed? (Current code)

      Yes  : Go to  2.

      No  : The circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

      NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
2. CHECK DTC  .

   Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC other than U0284 displayed? (Current code)

   Yes  : Check the appropriate DTC using the "Diagnostic Trouble Code (DTC)". Ref. to ENGINE (DIAGNOSTICS) (H4DO)>DIAGNOSTIC TROUBLE CODE (DTC) .

   No  : Go to  3.

3. CHECK HARNESS (GROUND SHORT CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the battery. Ref. to REPAIR CONTENTS>NOTE>BATTERY .
   3. Disconnect the connector from ECM.
   4. Measure the resistance between the ECM connector and engine ground.

      Connector terminal 

      (B134) No. 17 - Engine ground:

      Is the resistance 1 MΩ or more?

      Yes  : Go to  5.

      No  : Go to  4.

4. CHECK HARNESS BETWEEN ECM CONNECTOR AND EACH MODULE (SHORT TO GROUND)  .

   With a circuit tester connected to the ECM connector, disconnect each module in order.

   NOTE: Disconnect the connectors of active grille shutter, battery sensor, generator, DC/DC converter 1, and DC/DC converter 2 (model with power amplifier) in order.

   Connector terminal 

   (B134) No. 17 - Engine ground:

   Did the resistance change to 1 MΩ or more?

   Yes  : Replace the module whose resistance has changed.

   No  : Repair the short circuit to ground in harness between ECM and connector of each module.

5. CHECK HARNESS BETWEEN ECM CONNECTOR AND ACTIVE GRILLE SHUTTER CONNECTOR (OPEN)  .
   1. Disconnect the connector from the active grille shutter.
   2. Measure the resistance of harness between ECM connector and active grille shutter connector.

      Connector & terminal 

      (B134) No. 17 - (B63) No. 3:

      Is the resistance less than 10 Ω?

      Yes  : Go to  6.

      No  : Repair the following item.

      • Open circuit of harness between ECM and active grille shutter connector
      • Poor contact of coupling connector
6. CHECK ACTIVE GRILLE SHUTTER POWER SUPPLY  .
   1. Connect the battery. Ref. to REPAIR CONTENTS>NOTE>BATTERY .
   2. Measure the voltage between active grille shutter connector and engine ground.

      Connector & terminal 

      (B63) No. 2 (+) - Engine ground (-):

      Is the voltage 9 V or more?

      Yes  : Go to  7.

      No  : Repair the following item.

      • Open circuit or short circuit to ground in harness between active grille shutter connector and M/B
      • Poor contact of coupling connector
      • Blown out of fuse
7. CHECK HARNESS BETWEEN ACTIVE GRILLE SHUTTER CONNECTOR AND GROUND (OPEN)  .

   Measure the resistance of harness between active grille shutter connector and engine ground.

   Connector & terminal 

   (B63) No. 4 - Engine ground:

   Is the resistance less than 10 Ω?

   Yes  : Replace the active grille shutter. Ref. to COOLING (H4DO)>ACTIVE GRILLE SHUTTER .

   No  : Repair the following item.

   • Open circuit in harness between active grille shutter connector and ground
   • Poor contact of coupling connector