Parts
$0–80
P0456 — EVAP Very Small Leak Detected
SAFEIs it safe to drive? A very small vapor leak. No driving concern; emissions-test fail.
What P0456 means
A tiny EVAP leak — the system found a leak even smaller than the P0442 threshold. Almost always the cap or a hairline crack.
Most likely causes (in order)
- Gas cap seal
- Hairline crack in EVAP hose
- Weeping valve seal
Symptoms you might notice
- Check-engine light
What to check first
New gas cap, then a smoke test if it persists — this size leak is invisible without smoke.
Repair cost & difficulty
Labor
0.1–1 hr
Difficulty
Easy DIY