P0455: EVAP system large leak detected
The system that holds petrol vapour cannot build up vacuum, which points to a large leak. A fuel cap left loose is the classic cause.
| Code | P0455 |
|---|---|
| System | Engine and transmission |
| Group | P04xx, Emissions control |
| Type | Generic: it means the same on every make |
| Can you keep driving? | With care |
What P0455 means
From time to time the ECU seals the tank’s vapour circuit and checks whether it holds pressure or vacuum. When it gets nowhere near the target, it concludes there is a big leak, such as an open cap or a disconnected hose.
Most common causes
- Fuel cap loose, missing or with a damaged seal
- Vapour hose disconnected or split between tank, canister and engine
- Canister vent valve stuck open
- Purge valve not closing
- Cracked charcoal canister
- Corroded or damaged filler neck
Symptoms
- Engine warning light on
- Sometimes a smell of petrol around the car
- Usually no change in how it drives
Can you drive with P0455?
With care You can drive, but petrol vapour is escaping, and if the smell is strong it should be checked soon. The car will not pass inspection with this fault.
How to check it
Check the fuel cap first: it should click when tightened and its rubber seal should not be cracked. Clear the code and see whether it returns after a few days of normal driving.
How to read and clear P0455 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0455 with this same explanation and whether it’s confirmed, pending or permanent.
With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.
Similar codes
- P0451 EVAP pressure sensor range or performance problem
- P0452 EVAP pressure sensor circuit low
- P0453 EVAP pressure sensor circuit high
- P0454 EVAP system pressure sensor intermittent signal
- P0456 EVAP system very small leak detected
- P0457 EVAP system leak: fuel cap loose or missing
- P0458 EVAP purge control valve circuit low
- P0459 EVAP purge control valve circuit high
- P0400 Exhaust gas recirculation (EGR) flow malfunction
- P0401 Exhaust gas recirculation (EGR) flow insufficient
- P0402 Exhaust gas recirculation (EGR) flow excessive
- P0403 EGR control circuit malfunction
P0455 is a generic code, so it means the same on any make, for example on Audi, Dacia, Fiat, Kia, Opel / Vauxhall, Toyota. See what Final OBD does on your car in makes and models.
What does code P0455 mean?
From time to time the ECU seals the tank’s vapour circuit and checks whether it holds pressure or vacuum. When it gets nowhere near the target, it concludes there is a big leak, such as an open cap or a disconnected hose.
Can you drive with P0455?
You can drive, but petrol vapour is escaping, and if the smell is strong it should be checked soon. The car will not pass inspection with this fault.
How do you clear P0455?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0455 comes back.
Read it on your car
Final OBD reads the faults of every control unit for free, including each make’s own codes, and with Pro explains each one in plain English. Free clears engine faults at no cost.
Coming soon
Mid to late October 2026
If you want to try it in your car before anyone else, send us your email and we will add you as a tester.
info@finalobd.com