What P0457 means
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.
How the engine computer detects it
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 (−0.3 psi) 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.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check fuel cap lamp or check engine light on
- Fuel smell
- EVAP readiness not set
Common causes
- Fuel cap not closed, not clicked in or forgotten Most likely
- Fuel cap seal faulty or non-original cap Possible
- Filler neck sealing surface damaged or capless flap sticking Possible
- Vent valve stuck open Less likely
How to diagnose P0457
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: fuel cap, fuel filler neck, evap system.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Vehicles that report P0457 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Ford Fusion | 2010–2011 | 4 | — |
Counts of owner complaints to the NHTSA that mention P0457 (14 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 4
- Auxiliary emission controls
- 57
- Specific fault
Questions drivers ask
Can I drive with code P0457?
Usually yes for a short time, if the car drives normally, the temperature gauge reads normal and the check engine light is steady. If the light flashes, the engine loses power or overheats, or other warning lights come on, pull over and have it checked.
Will my car pass an emissions inspection with P0457?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P0457 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Can I fix P0457 myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: easy. Start with the cheapest checks before replacing expensive parts.
Often reported together
Codes that owners mention in the same NHTSA complaints as P0457. They can point to a shared cause, so it's worth checking them together.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.