What does P0456 mean?

The EVAP system has a very small leak, around 0.5 mm.

Why is P0456 hard to find?

The leak is tiny, so it often needs a smoke machine to locate.

Evaporative emission (EVAP)

P0456 — Evaporative Emission System Leak Detected (Very Small Leak)

The ECU found a very small leak in the EVAP system, around 0.5 mm. It is hard to locate and is often caused by a worn fuel cap seal or a small crack in a hose or seal.

Severity: Low

Common causes

Worn fuel cap seal
Tiny crack in an EVAP hose or fitting
Leaking purge or vent valve seal
Small canister or tank seal leak
Faulty fuel tank pressure sensor

Symptoms

Check engine light
Usually no other symptom
Failed emissions test
Faint fuel smell in some cases

How to check

Replace the fuel cap with a quality one, clear the code and drive for the EVAP monitor to rerun
Use a smoke machine to find tiny leaks
Inspect hose ends, seals and valves
Check the fuel tank pressure sensor

Can you keep driving?

Safe to drive. Repair it at your convenience; leak tests can take a few days of driving to complete.

Frequently asked questions

What does P0456 mean?: The EVAP system has a very small leak, around 0.5 mm.
Why is P0456 hard to find?: The leak is tiny, so it often needs a smoke machine to locate.

General reference information. It does not replace a diagnosis on your own vehicle. The same code can have different causes depending on make, model year and engine; check the manufacturer's documentation or ask a technician with a scan tool.