P0457EVAP System Leak Detected (fuel cap loose/off)
- 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. P0457 is a large leak attributed to the fuel cap: Ford detects refuelling and treats a vacuum that is not reached afterwards (about −2 kPa in 30 s) as an open cap. CARB allows a separate check fuel cap lamp instead of the warning lamp, and the code is cleared once the cap is found tight again. Ford sets the lamp after two to three trips depending on calibration, Subaru after two. GM and Saab's ME9 do not use the code.
- What you may notice
- Check fuel cap lamp or check engine light on
- Fuel smell
- EVAP readiness not set
- Likely causes
- LikelyFuel cap not closed, not clicked in or forgotten
- PossibleFuel cap seal faulty or non-original cap
- PossibleFiller neck sealing surface damaged or capless flap sticking
- RareVent valve stuck open
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €0 – €60
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.