Powertrain, generic · Auxiliary emission controls
P04FC Crankcase Ventilation System Performance
Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo
The crankcase ventilation routes blow-by gas into the intake, and CARB requires it to be monitored. P04FC is a general function check: pressure or flow in the system deviates from the model. FCA uses it on the 2.0-litre turbo in the Wrangler and Cherokee (2018–19) and the 3.6 Pentastar in the Challenger (2020), with known false triggers fixed by engine module software; the strategy is not published, a FCA patent evaluates a pressure sensor in the fresh-air line.
Likely causes
Module software (FCA false trigger)
PCV valve or oil separator blocked or sticking
Ventilation or fresh-air hose leaking or loose, oil filler cap leaking
Increased blow-by (piston rings)
Symptoms
- Check engine light on
- Possibly oil consumption or oil in the intake
- Whistling from false air
Repair estimate
DifficultyMediumWorkshop job
Parts and labour€0–600
Time0.3–3 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
pcv valveoil separatorcrankcase ventilation hoseengine control module
Related codes
References: static.nhtsa.gov, static.nhtsa.gov, patents.google.com, law.cornell.edu.