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.
Medium severity. Can I keep driving?You can drive in moderation. If oil consumption increases or there are leaks, check the level often and go to a repair shop soon.
Symptoms
- Check engine light on
- Possibly oil consumption or oil in the intake
- Whistling from false air
Most 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)
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P04FC means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 4: Emissions
- FC: Specific fault in that system
Frequently asked questions
Can I keep driving with code P04FC?
You can drive in moderation. If oil consumption increases or there are leaks, check the level often and go to a repair shop soon.
What causes code P04FC?
The most common causes are: 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.
Related codes
- P04DBCrankcase Ventilation System Disconnected
- P04FBCrankcase Ventilation Hose Connection Sensor Range/Performance
- P04E2Crankcase Ventilation Hose Connection Sensor Circuit Low
- P04E3Crankcase Ventilation Hose Connection Sensor Circuit High
- P2282Air Leak Between Throttle Body and Intake Valves
- P051ACrankcase Pressure Sensor A Circuit
Sources
- static.nhtsa.gov: MC 10170398 9999
- static.nhtsa.gov: MC 10181607 9999
- patents.google.com: US10043352
- law.cornell.edu: 13 CCR 1968.2
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.