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2005 18psi supercharged U5 Outback w/207k+ miles
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Discussion Starter · #1 ·
I noticed there is a switch in RomRaider logger that says "positive crankcase ventilation". I monitored it for a while and it never went to "1" (on).

Is this switch "active" on a regular 2.5i engine? I think I remember seeing an electrical connector on the turbo PCV assembly so maybe that is a real thing but just not on the NA 2.5i model?

Thanks.
 

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Yes, it is, but it isn't a real "switch". Rather, where the PCV hose is mounted to the front of the airbox, there's a two wire connector. When the hose is connected, a short in the hose bridges across the two pins of the connector. This signals the ECM that the hose is in place. In the attached photo, the hose coming up from the lower left (from the PCV fitting on the engine block) is fitted to the white piece that has the "short". The white piece fits into a tube on the front of the airbox. That tube dead-ends at the airbox, but has a rubber hose going down from it into the airbox. This is a passage for crankcase fumes into the intake. If the hose were disconnected, it would allow outside air to enter the crankcase and that would upset the fuel trim management.

The connector is described as "PCV hose assembly diagnosis signal - Blow-by Leak Diagnosis Connector".

If the connector is off, the OBD should generate a fault code:

DTC P1491 POSITIVE CRANKCASE VENTILATION (BLOW-BY) FUNCTION PROBLEM
1. OUTLINE OF DIAGNOSIS
Detect the blow-by hose release abnormality.
Judge as NG when the diagnosis terminal voltage is high.
 

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2005 18psi supercharged U5 Outback w/207k+ miles
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843 Posts
Discussion Starter · #3 ·
Ahhh ok, thank you. I don't have that connector, just hoses and clamps on the 05. I was hoping there was actually something that told you when the PCV was open vs closed. That would be sort of cool.
 

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'17 3.6R Touring Brillant Brown Pearl
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The only time the pcv is closed is in a backfire situation.
 
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