P0440 — Evaporative Emission (EVAP) System Malfunction
Can drive — fix at your convenience.
What P0440 means
P0440 is a broad code indicating the EVAP system, which traps gasoline vapors and routes them back to the engine instead of releasing them into the air, isn't sealing or working as it should. Because it's a general code, the cause can range from a bad gas cap to a leaking hose or a faulty valve. It rarely affects how the car runs, but it does signal a leak of fuel vapor.
Common symptoms
- Check engine light is on
- A faint smell of gasoline near the vehicle
- Failed emissions or smog test
- No noticeable change in how the car drives
- Slightly reduced fuel economy in some cases
Common causes
- Loose, missing, or damaged gas cap
- Cracked or disconnected EVAP hose
- Faulty purge valve or vent valve
- Leaking or damaged charcoal canister
- Bad seal on the gas cap or filler neck
Typical repair cost
$20 – $300
Varies by vehicle and root cause.
Frequently asked questions
Is it just the gas cap?
Very often, yes. A loose or worn gas cap is the most common and cheapest cause of P0440. Try tightening it until it clicks, and if the light stays on after a few drives, replacing the cap (about $20-60) is a smart first step before paying for deeper diagnosis.
Can I drive with a P0440 code?
In nearly all cases, yes. The car will run normally and it's safe to drive short to medium distances. Just get it inspected soon, since the issue won't fix itself and the warning light will stay on.
How much does it cost to fix?
If it's just the gas cap, you're looking at $20-60. A leaking hose, purge valve, or vent valve repair typically runs $100-300 including labor and diagnosis.
Is P0440 a serious problem?
It's usually low severity. It doesn't damage the engine and won't leave you stranded, but it does let fuel vapors escape and will cause an emissions failure, so it's worth fixing.