P04DFEVAP System Purge Control Valve A Performance/Stuck Open
- 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
- Purge valve A is the main EVAP purge valve between charcoal canister and intake manifold (on turbo engines the low-load path); its electrical circuit faults are P0443, P0458 and P0459. No manufacturer document available to us uses this code; the description follows GM's comparable check P0496, Subaru's valve B counterpart P04AE and CARB's purge flow requirement. P04DF means valve A does not react as commanded or lets vapour through when closed: with the system sealed and the valve not driven, vacuum must not reach the tank. Intake vacuum then draws vapour all the time – rich mixture and hard starting after refuelling are typical.
- What you may notice
- Check engine light on
- Hard starting or stumbling idle right after refuelling
- Rough idle, rich fuel trim
- Likely causes
- LikelyPurge valve A leaking or stuck open (charcoal dust or dirt on the seat)
- PossibleCanister broken down, charcoal dust in the valve
- RareTank pressure sensor giving a wrong signal
- RareHoses swapped or wrongly routed
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €40 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.