P0440: There is a general fault in the fuel vapor containment system
Evaporative Emission Control System Malfunction
There is a fault in the fuel vapor (EVAP) system. Check that the gas cap is tight, then get it checked within a couple of weeks. If you smell strong gas, get it checked right away.
Stop driving and get help if
- The check engine light is flashing
- The temperature gauge runs high, or you see steam (overheating)
- The car loses power, hesitates badly or stalls
- You smell burning or see smoke
- A brake warning light comes on, or the brakes feel different
Pull over as soon as you can, turn the engine off, and call a tow or roadside help.
What it means
The evaporative emission system traps fuel vapors from the gas tank and routes them into the engine to be burned. The computer tests the system by sealing it and checking whether pressure holds. P0440 is a general flag that something in the EVAP system is not working right, but it does not tell you where the leak or fault is. Think of it as the system's way of saying something is wrong without pinpointing which component. More specific codes like P0441 or P0446 are usually stored alongside it and are more useful for diagnosis.
Common causes
- Loose, missing, or cracked gas capThe single most common cause. Always start here before doing anything else.
- Faulty purge valve or vent valveEither valve stuck open or closed prevents proper EVAP system sealing.
- Cracked or disconnected EVAP hosesRubber hoses connecting the canister and fuel tank become brittle with age.
- Failing charcoal canisterThe canister that stores fuel vapors can crack or become saturated.
What the fix could involve
From the cheaper fix to the bigger one. Prices depend on your car, your area and the shop, so ask for a written quote that names the part and the labor before you approve it.
- Gas cap replacement
- Purge or vent valve replacement
- Charcoal canister replacement
Symptoms
- Check engine light on
- Faint fuel smell near the car, especially after parking
- No change in how the car drives
- Failed emissions test
What to do next
Start with the gas cap. Remove it, inspect it for cracks in the rubber seal, and reinstall it firmly until it clicks. Drive a full cycle and see if the code returns. If it does, look for more specific companion codes to guide diagnosis. A shop can perform a smoke test to find any leak in the system.
Lewis shows you any companion EVAP codes that are stored alongside P0440, which is often the fastest way to narrow down where in the system the fault is. Get Lewis on the App Store or Google Play.
Related codes
FAQ
- Is it safe to keep driving with P0440?
- It is an emissions fault, and the car usually runs normally. Check that the gas cap is tight, then get it checked within a couple of weeks. If you smell strong gas, get it checked right away.
- How long can I wait to fix it?
- Get it checked within a couple of weeks. You will fail emissions testing until it is fixed, and a fuel smell means get it checked right away.
- Why does the fuel smell appear?
- A leak in the EVAP system allows raw fuel vapors to escape from the tank or lines instead of being routed into the engine.
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