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.
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?
- Loose, missing or worn gas cap~50%
- Faulty vent valve~20%
- Faulty purge valve~15%
- Cracked EVAP hose~10%
- Charcoal canister problem~5%
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):
| New gas cap | $5 – $25 |
| Vent or purge valve | $80 – $200 |
| EVAP hose | $50 – $150 |
| Smoke test | $50 – $150 |
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 gas caps & OBD-II scanners ›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 $5-$25 for a gas cap or up to a few hundred dollars for a valve or hose.
Related codes
General guidance based on the standard definition of the P0440 code. A real diagnosis depends on your make, model, mileage and other symptoms. When in doubt, have a professional confirm the cause before replacing expensive parts.