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P0440 P0xxx · 动力总成（P） 低严重度
Evaporative Emission Control System Malfunction
The EVAP system failed its overall integrity check. Fuel vapour is escaping somewhere between the tank and the charcoal canister.
严重程度说明： 低——通常不影响行驶，下次保养时处理即可
你会注意到的故障现象
- Fuel smell around the vehicle
- Check-engine light
- Failed emissions test
- Occasional rough idle after refuelling
常见原因
按可能性从高到低排列——从最上面开始查。
- 1 Loose, missing or damaged fuel cap
- 2 Cracked vapour hose
- 3 Failed purge or vent solenoid
- 4 Leaking charcoal canister or tank seal
如何排查
先做花钱最少、侵入最小的检查——大多数这类码不是零件问题。
- ✓ Check the fuel cap first — it is the single most common cause and costs nothing.
- ✓ Smoke-test the EVAP system at the service port; leaks show up in seconds.
- ✓ Command the purge and vent solenoids with a scan tool and confirm they hold vacuum.
- ✓ Inspect the filler neck and tank seam for rust.
维修方案
- Replace the fuel cap
- Repair the leaking hose or seal
- Replace the vent or purge solenoid
P0440 —— 常见问题
Is it dangerous to drive? +
Generally not, but a large leak is a fire risk and will fail inspection. Fix it reasonably soon.
Why does it come back after refuelling? +
A cap that does not seal or a damaged filler neck — the system detects the leak right after the tank is opened.