Your IP address and browser information will be recorded as proof of this acknowledgement. This data is retained for 12 months.
The engine management light or check engine light illuminates due to an evaporative emission system leak caused by a loose or missing fuel filler cap. The EVAP system is pressurised and any leak triggers the P0440 to P0449 range of fault codes. Tightening or replacing the fuel filler cap and clearing the code with an OBD reader resolves the fault. Always check the fuel cap first before spending money on EVAP system components.
Based on 684 driver confirmations
No commonly reported misdiagnoses for this fault yet. If you have replaced a part that did not fix this problem, submit a wrong diagnosis report — it helps other drivers avoid the same costly mistake.
Fuel cap was fine. Code was P0442 small evap leak. Mechanic smoke tested the system and found the purge valve wasn't sealing. Replaced it. Not an expensive part but you need the smoke test to find it — don't just guess.
Parts replaced: EVAP purge solenoid valve
Fuel cap was tight but light kept coming back every few weeks. Eventually bought a new OEM cap — the rubber seal on the old one had gone hard and cracked, wasn't sealing properly. £22 for a genuine cap, light never came back. The evap system leak code P0457 was stored.
Parts replaced: Fuel filler cap (OEM)
EML came on, no other symptoms, car running fine. Googled it and saw fuel cap is a common cause. Checked mine and it wasn't clicked fully shut. Tightened it properly, drove the next day and the light had cleared itself. Felt a bit stupid but saved myself a garage visit. Always try this first before panicking.
Parts replaced: Nothing
Your real-world fix helps thousands of drivers worldwide. Takes 2 minutes.