P0440 Evaporative emission (EVAP) system malfunction
What P0440 means
The engine computer runs a self-test on the sealed system that traps fuel vapour from the tank and later burns it in the engine. P0440 means that test found a general fault: the system is leaking or a valve is not working as commanded. It does not affect how the engine runs, but it does raise evaporative emissions and can fail a technical inspection.
P0440 is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- Low
- Typical repair cost
- 30–350 €
- Workshop time
- 0.2–2.5 h
- Repair difficulty
- Easy
- DIY possible
- Yes
- Check engine light
- Yes
- Affects emissions test
- Yes
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Check engine light on
- Faint fuel smell near the filler or tank
- Car otherwise drives normally
- Technical inspection failure for emissions
Common causes
- Fuel cap loose, missing or with a worn seal
- Cracked or disconnected EVAP hose
- Faulty canister purge valve
- Faulty canister vent valve or blocked vent filter
- Leaking charcoal canister or filler neck
Can I keep driving with P0440?
Yes, you can keep driving; this is an emissions fault, not an engine-damage risk. Tighten the fuel cap first and have the system checked within a week or two if the light does not go out.
What to check first
- Check the fuel cap: remove it, inspect the rubber seal, refit until it clicks, then clear the code and drive for a few days
- Look for cracked, chafed or disconnected EVAP hoses around the canister, tank and engine bay
- Test the purge and vent valves: they should click when commanded and hold vacuum when closed
- If nothing is visible, have a smoke test done to locate the leak
Related codes
- P0441 EVAP system incorrect purge flow
- P043F EVAP leak detection reference orifice high flow
- P0442 EVAP system small leak detected
- P043E EVAP leak detection reference orifice low flow
- P0443 EVAP purge control valve A circuit
- P0446 EVAP vent control circuit
- P0449 EVAP vent valve control circuit/open
- P0431 Warm-up catalyst efficiency below threshold (bank 2)
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
Updated: