P0457
Low severityEvaporative Emission System Leak Detected (Fuel Cap Loose/Off)
P0457 almost always means the gas cap is loose, missing or not sealing. The car drives normally, but it will fail an emissions or smog test until the code clears. Check the cap first — it’s often a free fix.
Stop driving if: you smell strong raw fuel, or see fuel leaking under the car.
What does the P0457 code mean?
The P0457 code means your car’s computer detected a leak in the EVAP system and specifically suspects the fuel cap is loose or off. The EVAP system keeps fuel vapour from escaping the tank. Several times per drive cycle, the computer seals it and checks whether it holds pressure or vacuum. If it can’t, and the pattern looks like an open filler, it sets P0457.
Many cars set this code right after refuelling, when the cap wasn’t tightened until it clicked — or was left on the pump. It’s closely related to P0455 (large EVAP leak).
Can you keep driving with a P0457 code?
Yes. P0457 doesn’t affect how the engine runs and won’t cause damage. You’ll lose a little fuel to evaporation and you’ll fail an emissions inspection while the code is active. Tighten or replace the cap, and the light will usually switch off on its own after several days of normal driving.
What causes a P0457 code?
Listed in the order most shops would check them — cheapest and most likely first, not as statistical odds. The real cause varies by year, make, model and engine.
- Gas cap loose, missing or not clicked tightCheck 1st
- Worn or cracked gas cap sealCheck 2nd
- Damaged or corroded fuel filler neckCheck 3rd
- Leak in an EVAP hose, purge valve or vent valveCheck last
Many newer Fords and some GM vehicles use a capless fuel filler with a spring-loaded flap instead of a cap. On these, P0457 usually means dirt is keeping the flap from sealing, or a fuel nozzle didn’t seat fully. Use the plastic funnel supplied with the car to open and close the flap a few times, and clean around the seal.
How to diagnose a P0457 (check these first)
This is one of the cheapest codes to fix — check in this order:
- Remove the gas cap and reinstall it, turning until it clicks at least once. Make sure nothing is caught under the seal.
- Inspect the cap’s rubber seal for cracks, flattening or tears. If it looks worn, a new cap is inexpensive.
- Look at the lip of the filler neck for rust, dents or debris that would stop the cap from sealing.
- Clear the code (or wait several drive cycles) and see if it returns. If it comes back with a good cap, have a shop smoke-test the EVAP system to find the real leak.
P0457 repair cost
Costs vary a lot by vehicle and region. These are typical US ranges including parts and labor — treat them as a ballpark for the conversation with your shop, not a quote.
| Tighten or reseat the gas cap | $0 |
| Replacement gas cap | $15 – $40 |
| EVAP smoke test (diagnosis) | $100 – $150 |
| Fuel filler neck replacement | $150 – $300 |
Tools & parts that help
If your cap’s seal is worn, a replacement cap for your exact vehicle is one of the cheapest fixes in car repair. A basic OBD-II scanner lets you clear the code afterwards instead of waiting days for the light to switch off on its own.
See top-rated OBD-II scanners ›As an Amazon Associate I earn from qualifying purchases. This costs you nothing extra and never changes what we recommend.
P0457 — Frequently asked questions
Is it safe to drive with a P0457 code?
Yes. It does not affect how the engine runs. You will lose a little fuel vapour and fail an emissions test until it is fixed.
How long does it take for the light to go off after tightening the gas cap?
Usually a few days of normal driving. The computer has to re-run its EVAP self-test, which only happens under certain conditions such as a cold start and a steady drive.
What’s the difference between P0455 and P0457?
Both mean a large EVAP leak. P0457 specifically flags the fuel cap as the likely cause, while P0455 is a general large-leak code.
How much does it cost to fix a P0457?
Often nothing — just tighten the cap. A new gas cap costs about $15 to $40. If the leak is elsewhere, a smoke test and repair can run $100 to $300.
Related codes
General guidance based on the standard SAE definition of the P0457 code. A real diagnosis depends on your make, model, year, engine and other symptoms. This is not a substitute for a professional inspection — when in doubt, have a technician confirm the cause before replacing expensive parts.