Evap system has a leak.
P0440 — also written PO44O, P 0440, 0440 — is the OBD-II code for evaporative emission control system. Same code, same fix: this page covers every spelling of it.
P0440 means your car’s noticed it can't hold a vacuum in the petrol vapour system—usually a leaky pipe or a dodgy petrol cap seal. It's properly common on older Vauxhalls and Fords that have spent years on salted UK roads.
P0440 is a emissions fault code, typically costing £20–£350 to put right in a UK garage.
What P0440 actually feels like to drive
- The 'Check Engine' light is glowing on the dash, usually about 20 miles after you've filled up.
- A faint whiff of raw petrol when you're standing near the rear wheel arch after a long drive.
- The car might take a few extra cranks to start right after you've put fuel in at the Morrisons petrol station.
- A slight 'hiss' or sometimes no 'hiss' at all when you unscrew the filler cap (indicating no pressure).
- Passed the MOT emissions test perfectly, but the light is still staring you in the face.
What causes P0440?
- Loose fuel cap
- Cracked vent line
- Failed purge valve
UK vehicles that throw P0440 most often
- Vauxhall Corsa D/E 1.2 & 1.4 (2006-2019)
- Ford Fiesta Mk7 1.25 & 1.6 Ti-VCT (2008-2017)
- Vauxhall Astra J/K 1.4 Turbo (A14NET engine)
- Toyota Yaris 1.33 VVT-i (1NR-FE engine)
- Nissan Qashqai J10 1.6 Petrol (HR16DE)
- Honda Civic 1.4/1.8 i-VTEC (2006-2015)
How P0440 is fixed
- Tighten/replace fuel cap
- Smoke test evap
- Replace purge valve
The P0440 misdiagnosis that wastes money
I’ve lost count of how many times I’ve seen some lad at a 'fast-fit' centre throw a brand new £50 Bosch purge valve at a Vauxhall Astra just because P0440 popped up on his scanner. Nine times out of ten, they’re ignoring the most basic culprit: the petrol cap seal. I’ve had cars come in where the owner’s spent £200 on valves and charcoal canisters, only for me to find a tiny bit of grit or a perished rubber O-ring on the fuel filler cap. People always assume it’s a 'sensor fault' when it's actually just a physical air leak.
What a UK garage should charge for P0440
An initial diagnostic plug-in usually runs you £40-£60. If it's just the fuel cap, a genuine replacement from the dealer is about £20-£30. A purge valve (the bit that clicks under the bonnet) is around £40-£80 from Euro Car Parts or GSF. However, if I have to drop the fuel tank to find a corroded vent pipe, you’re looking at 3 hours of labour, which pushes the bill toward £300. Main dealers will easily double these prices with their £150+ hourly rates.
P0440 repair cost in the UK
Most P0440 repairs land between £20–£350 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Bob's tip on P0440
Don't let a garage just 'clear the code and see'—it’ll be back the minute the ECU runs its self-test. Insist on a 'smoke test'. We hook up a machine that pumps thick, white smoke into the EVAP lines at low pressure; if there's a pinhole leak in a pipe over the fuel tank or a cracked seam on the canister, the smoke shows us exactly where it is in minutes. Also, ask them to check the 'fuel tank pressure sensor' live data. If they don't know what that is, find an independent who specializes in diagnostics. It’ll save you paying for parts you don't need.
Can you drive with P0440?
Drivable.
Urgency: low.