OBD-II code · Powertrain (generic)
P04AF EVAP System Purge Control Valve B Stuck Closed
Same as P04AE but the valve B is stuck closed - no vapor purge possible through this stage, leading to elevated tank pressure and possible canister saturation.
Is it safe to drive with P04AF?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyValve stuck closed
- Less likelyCarbon or debris buildup preventing free movement
- Less likelyComponent wear with age - mechanical play
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
- 0.6–1.5 h
- Emissions test
- Likely to fail
- Parts involved
- Evap Purge Valve B
Related codes
- P04E0EVAP System Purge Control Valve A Stuck Closed
- P04ACEVAP System Purge Control Valve B Circuit Low
- P04ADEVAP System Purge Control Valve B Circuit High
- P04AEEVAP System Purge Control Valve B Performance Stuck Open
- P04B0Refueling Vapor Control Valve Circuit Open
- P04B1Refueling Vapor Control Valve Circuit Low
- P04B2Refueling Vapor Control Valve Circuit High
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.