P0456: Evaporative Emission System Leak Detected — Very Small Leak
What to do
Driveable with no symptom. Try a new fuel cap first and then drive it for several days — this monitor only runs under particular conditions, so an immediate re-check tells you nothing either way.
What this code means
The smallest leak the system can resolve, conventionally around half a millimetre. At this size nothing can be seen, heard or smelled, and the only practical method is smoke testing with the system properly sealed.
Two things are worth knowing before spending money. First, the test runs only under specific conditions — a particular fuel level range, stable temperature, and an undisturbed vehicle — so the code may take several drive cycles to reappear or to clear, and an immediate re-scan after a repair proves nothing. Second, a hardened fuel cap seal is still the most common single cause even at this size, and a cap is the cheapest part in the system.
Likely causes
Start here
- Loose or missing fuel filler cap · easy
- Cracked or perished EVAP hose · moderate
Less common
- Leaking filler neck seal · moderate
- Leaking purge valve seal · easy
- Cracked charcoal canister · moderate
- Faulty EVAP vent valve · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about P0456.