P04FC
Crankcase Ventilation System Performance
A general performance fault of the crankcase ventilation system - PCV pressure or flow does not match the engine model. Possible causes are a clogged PCV valve, blocked separator, oil-filler cap with a damaged seal, or excessive blow-by from worn rings.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- PCV valve clogged or stuckCommon
- Oil separator cloggedPossible
- Excessive blow-by from worn piston ringsLess likely
Parts involved
- PCV Valve
- Oil Separator
- Oil Filler Cap
P04FC is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.