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

1. - 

DTC detecting condition: 

Immediately at fault recognition

Trouble symptom: 

Improper idling

Wiring diagram: 

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

G13629887Courtesy of SUBARU OF AMERICA, INC.
CAUTION:

Use the check board when measuring the ECM terminal voltage and resistance. Ref. to  ENGINE (DIAGNOSTICS) (H4DOTC)>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD  . 

NOTE:

After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to  ENGINE (DIAGNOSTICS) (H4DOTC)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE  . 

  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 

      (E51) No. 22 - (E79) No. 2:

      (E52) No. 12 - (E79) 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 

    (E51) No. 22 - Engine ground:

    (E52) 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 .

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