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

DTC detecting condition: 

Immediately at fault recognition

Trouble symptom: 

Improper idling

Wiring diagram: 

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

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 BLOW-BY DIAGNOSIS CONNECTOR (OPEN). 
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from ECM.
   3. Disconnect the connector from blow-by diagnosis connector.
   4. Measure the resistance of harness between ECM connector and blow-by diagnosis connector.

      Connector and terminal. 

      (E158) No. 22 - (E110) No. 2:

      (E159) No. 12 - (E110) No. 1:

   Is the resistance less than 1 Ω?

   Yes:  Go to  3.

   No:  Repair the following item.

   • Open circuit in harness between ECM connector and blow-by diagnosis connector
   • Poor contact of coupling connector
   • Poor contact of J/C
3. CHECK HARNESS BETWEEN ECM AND BLOW-BY DIAGNOSIS CONNECTOR (SHORT TO GROUND). 

   Measure the resistance between the blow-by diagnosis connector and engine ground.

   Connector and terminal. 

   (E158) No. 22 - Engine ground:

   (E159) No. 12 - Engine 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 blow-by diagnosis connector.

4. CHECK PCV HOSE ASSEMBLY. 

   Measure the resistance between blow-by diagnosis connector terminals.

   Terminals. 

   No. 1 - No. 2:

   Is the resistance less than 1 Ω?

   Yes:  Repair the poor contact of ECM and blow-by diagnosis connector.

   No:  Replace the PCV hose assembly. Ref. to EMISSION CONTROL (AUX. EMISSION CONTROL DEVICES) (H4DOTC)>PCV HOSE ASSEMBLY .