P04B3
Refueling Vapor Control Valve Performance Stuck Open
The refueling vapor control valve is stuck open. Vapor pathways meant to be closed except during refueling stay permanently open, distorting EVAP leak diagnostics and allowing vapor flow even with the fuel cap closed.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Valve stuck open due to debris or weak springCommon
- Carbon or debris buildup preventing free movementLess likely
- Component wear with age - mechanical playLess likely
Parts involved
- Refueling Vapor Valve
P04B3 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.