P04B3Refueling Vapor Control Valve 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
- 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). P04B3 is the function check: with the valve commanded closed, tank and canister must not equalise their pressure; if the tank pressure follows the canister, for example during purging or the leak test, the valve is stuck open. Ford checks its comparable tank isolation valve under P2450 via the pressure ratio between tank and canister. Daily evaporation then loads the canister, which hybrids with little engine running time cannot purge enough. 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
- Fuel smell
- EVAP readiness not set
- Likely causes
- LikelyValve leaking or stuck open (dirt, wear)
- PossibleTank pressure sensor reading wrong
- RareLine at the valve swapped or damaged
- RareControl module software
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €100 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.