OBD-II code · Powertrain (generic, extended)
P2421 EVAP Vent Valve Stuck Open
The evaporative emission system vent valve does not close on command. The ECU detects that the evap system cannot hold pressure or vacuum because the canister is permanently vented to atmosphere.
Is it safe to drive with P2421?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyVent valve mechanically stuck open
- PossibleDust/debris preventing valve seat
- Less likelyCarbon or debris buildup preventing free movement
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
- 0.3–1 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Evap Vent Valve, Evap Canister
Related codes
- P241EReductant Heater Coolant Control Valve Stuck Closed
- P241FEGR Cooler B Efficiency Below Threshold
- P2420EVAP Switching Valve Stuck Closed
- P2422EVAP Canister Vent Valve Stuck Closed
- P2423HC Adsorption Catalyst Efficiency Below Threshold Bank 1
- P2424HC Adsorption Catalyst Efficiency Below Threshold Bank 2
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.