P04EFEVAP System Very Small Leak Detected - Fresh Air Side
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Hybrids with a sealed fuel tank have a valve separating the tank from the charcoal canister and its vent side. CARB allows such sections to be leak-checked separately with their own codes; a Ford patent checks the tank side via tank pressure with the valve closed and the canister side with a leak check module. Conventional systems report the same leak as P0442, P0455 or P0456. P04EF reports a very small leak (0.020 in) in the canister and vent section; the leak check module compares the vacuum against a 0.020 in reference and the section does not reach it. On Ford's C-Max, Fusion and MKZ hybrids and Energi a leaking purge valve is the typical trigger, fixed per bulletin with the valve and software.
- What you may notice
- Check engine light on
- EVAP readiness not set
- No change in driving
- Likely causes
- LikelyPurge valve not sealing
- PossibleVent valve or leak check module leaking
- PossibleHairline crack or leaking connections at the canister
- RareModule software (misjudgement)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €40 – €350
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.