Powertrain, generic · Vehicle speed, idle control and auxiliary inputs
P051F PCV Filter Restriction
Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo
The crankcase ventilation has an oil mist separator or filter element that can clog; the crankcase pressure sensor then sees rising pressure at a given flow. P051F reports this restriction. No manufacturer document available to us uses it – Ford reports high pressure under P051B. BMW and GM bulletins describe the consequences of a blocked separator: oil pushed past seals, oil mist in the intake and charge air cooler, higher oil consumption. CARB requires the PCV system to be monitored.
Likely causes
Separator or filter clogged with oil, soot or sludge
Icing in the separator or hose on short winter trips
Oil change intervals exceeded (sludge)
Pressure sensor reading wrong
Symptoms
- Check engine light on
- Oil leaks at seals or dipstick
- Oil mist in the intake, higher oil consumption
Repair estimate
DifficultyMediumDIY possible
Parts and labour€30–400
Time0.5–3 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
pcv filteroil separatorcrankcase pressure sensorengine control module
Related codes
References: law.cornell.edu, static.nhtsa.gov, static.nhtsa.gov.