P04B1Refueling Vapor Control Valve Circuit Low
- 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
- The evaporative emission (EVAP) system stores fuel vapour from the tank in a charcoal canister; a purge valve lets the engine draw it off, and a vent valve opens the canister to fresh air. Plug-in hybrids and range extenders with a sealed, pressurised tank have an electric valve in the vapour line between tank and canister. It is normally closed and opens before refuelling, so that the tank is depressurised – the filler flap is only released then – and refuelling vapour reaches the canister (Ford patent). P04B1 means the control wire is shorted to ground, so the valve is permanently energised. With a normally closed valve the tank is then always connected to the canister: daily evaporation loads the canister and the tank cannot be sealed for the leak test. No manufacturer document available to us uses this code – Ford reports its tank isolation valve as P2418/P2450 – so the description follows CARB and the component patent.
- What you may notice
- Check engine light on
- Possibly fuel smell
- EVAP readiness not set
- Likely causes
- LikelyControl wire chafed against ground (underbody, tank area)
- PossibleValve coil shorted internally
- PossibleMoisture in the connector
- RareDriver in the control module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €50 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.