P0440
Low severityEvaporative Emission Control System Malfunction
Safe to drive. P0440 is the generic EVAP system code — it doesn’t specify what’s wrong, just that something is off. Start with the gas cap.
Stop driving if: the check engine light is flashing, or the car starts running noticeably worse
What does the P0440 code mean?
The P0440 code is a general “EVAP system malfunction” code. Unlike P0455, P0442 or P0456 (which specify large, small or very small leaks), P0440 just says something is wrong in the EVAP system.
It’s more common on older vehicles (pre-2002 OBD-II). The most likely causes are the same as the other EVAP codes: a gas cap problem first, then hoses, valves or the charcoal canister.
Can you keep driving with a P0440 code?
Yes. P0440 doesn’t affect how the engine runs. The car will fail an emissions inspection until it’s fixed, but otherwise drive normally.
What causes a P0440 code?
Listed in the order most shops would check them — cheapest and most likely first, not as statistical odds. The real cause varies by year, make, model and engine.
- Charcoal canister problemCheck 1st
- Cracked EVAP hoseCheck 2nd
- Faulty purge valveCheck 3rd
- Faulty vent valveCheck last
How to diagnose a P0440 (check these first)
- Tighten the gas cap and drive a few cycles to see if the light clears.
- Replace the gas cap if it’s old or the seal looks worn.
- Have a shop run a smoke test if it persists — it pinpoints the leak fast.
- Check that EVAP hoses near the tank and engine are intact.
P0440 repair cost
Typical US ranges including parts and labor (varies by vehicle):
Costs vary a lot by vehicle and region. These are typical US ranges including parts and labor — treat them as a ballpark for the conversation with your shop, not a quote.
| New gas cap | – |
| Vent or purge valve | – 0 |
| EVAP hose | – 0 |
| Smoke test | – 0 |
Tools & parts that help
Start with a fresh gas cap for your vehicle and a basic OBD-II scanner so you can clear the code yourself after the fix.
See top-rated OBD-II scanners ›As an Amazon Associate I earn from qualifying purchases. This costs you nothing extra and never changes what we recommend.
P0440 — Frequently asked questions
Is it safe to drive with a P0440 code?
Yes, the engine runs normally. The car will fail emissions until it’s fixed.
What’s the difference between P0440 and P0455?
P0455 specifies a large EVAP leak. P0440 is the generic EVAP fault code, more common on older vehicles, and doesn’t tell you the leak size.
Will tightening the gas cap fix P0440?
Often yes – it’s the most common cause. Tighten until it clicks several times and drive a few cycles.
How much to fix P0440?
Typically – for a gas cap or up to a few hundred dollars for a valve or hose.
Related codes
General guidance based on the standard SAE definition of the P0440 code. A real diagnosis depends on your make, model, year, engine and other symptoms. This is not a substitute for a professional inspection — when in doubt, have a technician confirm the cause before replacing expensive parts.