What it means
The EVAP system detected a large leak that strongly correlates with a missing or improperly closed fuel filler cap. After re-tightening the cap, the code clears once the readiness monitor completes.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The EVAP system seals fuel vapors in the tank and routes them through a canister to the engine. P0457 indicates the system detected a leak consistent with a loose or missing fuel cap, though a worn cap seal or damaged filler neck can also prevent a proper seal.
Common causes
Most likely first.
- Fuel cap loose, missing, or worn seal
- Filler neck damaged
Symptoms
- Check engine light on
- Possible smell of fuel near tank or engine bay
- Failed emissions inspection
- Loose-cap warning may appear
How to diagnose it
- Check freeze-frame and EVAP monitor data, then verify whether the fuel cap is missing or was left loose after refueling.
- Inspect the cap seal and filler-neck rim for dirt, cracks, deformation, or damage that could prevent sealing.
- Refit the cap and make sure it engages and tightens as designed, then check whether the loose-cap warning or code returns after the monitor runs.
- If the cap and filler neck appear sound, inspect nearby EVAP hoses and connections for a larger leak.
- Use the manufacturer's EVAP leak-test procedure to confirm the leak source before replacing valves or other components.
Common fixes
- Refit and properly secure the existing fuel cap.
- Replace a missing cap or one with a damaged seal.
- Repair a damaged filler neck or sealing surface.
- Repair any confirmed leak in an EVAP hose, connection, or valve.
Can I keep driving?
You can usually drive after securing the cap if there is no fuel leak or strong fuel odor, but the warning may remain until the EVAP monitor completes. An unsealed system can release fuel vapor and cause an emissions-test failure.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.