OBD-II code · Powertrain (generic)
P04EF EVAP System Very Small Leak Detected Fresh Air Side
Same as P04EE on the fresh-air side - microcrack in a hose or imperfect vent valve seal at the most sensitive test threshold.
Is it safe to drive with P04EF?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyVent valve seal aged
Symptoms
- Check engine light on
- Possible smell of fuel near tank or engine bay
- Failed emissions inspection
- Loose-cap warning may appear
Repair at a glance
- Difficulty
- Easy
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.4–1.2 h
- Emissions test
- Likely to fail
- Parts involved
- Evap Vent Valve, Evap Hose Fresh Air Side
Related codes
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.