DTC P04DB: Crankcase Ventilation System (PCV) Disconnected: Notes

DTC detecting condition: 

Immediately at fault recognition

Trouble symptom: 

Improper idling

Wiring diagram: 

Engine Electrical System Refer to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK BLOW-BY HOSE. 

   Check the blow-by hose condition.

   Is there any disconnection or crack in blow-by hose?

   Yes:  Install or replace the blow-by hose.

   No:  Go to  2.

2. CHECK HARNESS BETWEEN ECM AND PCV HOSE ASSEMBLY CONNECTOR. 
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from ECM.
   3. Disconnect the connector from the PCV hose assembly.
   4. Measure the resistance of harness between ECM connector and PCV hose assembly connector.

   Connector & terminal 

   (B137) No. 12 - (E80) No. 2:

   Is the resistance less than 1 Ω?

   Yes:  Go to  3.

   No:  Repair the harness and connector.

   NOTE: In this case, repair the following item:

   • Open circuit in harness between ECM connector and PCV hose assembly connector
   • Poor contact of coupling connector
3. CHECK HARNESS BETWEEN ECM AND PCV HOSE ASSEMBLY CONNECTOR. 

   Measure the resistance between PCV hose assembly connector and chassis ground.

   Connector & terminal 

   (B137) No. 12 - Chassis ground:

   Is the resistance 1 MΩ or more?

   Yes:  Go to  4.

   No:  Repair the short circuit to ground in harness between ECM connector and PCV hose assembly connector.

4. CHECK HARNESS BETWEEN LEAK DIAGNOSIS CONNECTORS. 

   Measure the resistance of harness between each of leak diagnosis connector.

   Connector & terminal 

   (E80) No. 1 - (E87) No. 1:

   (E87) No. 2 - (E88) No. 1:

   (E88) No. 2 - (E98) No. 1:

   (E98) No. 2 - (E99) No. 1:

   (E99) No. 2 - (E100) No. 1:

   Is the resistance less than 1 Ω?

   Yes:  Go to  5.

   No:  Repair the open circuit in the wiring harness between leak diagnosis connectors.

5. CHECK GROUND CIRCUIT OF PCV HOSE ASSEMBLY. 

   Measure the resistance of harness between PCV hose assembly connector and engine ground.

   Connector & terminal 

   (E87) No. 2 - Engine ground:

   Is the resistance less than 5 Ω?

   Yes:  Go to  6.

   No:  Repair the open circuit in harness between PCV hose assembly connector and engine ground.

6. CHECK PCV HOSE ASSEMBLY. 

   Measure the resistance between terminals of each leak diagnosis connector.

   Terminals 

   No. 1 - No. 2:

   Is the resistance less than 1 Ω at all measurement?

   Yes:  Repair the poor contact of ECM and PCV hose assembly connector.

   No:  Replace the PCV hose assembly. Refer to EMISSION CONTROL (AUX. EMISSION CONTROL DEVICES) (STI)>PCV HOSE ASSEMBLY .