EVAP system gross leak on BMW — fuel cap, purge valve and the leak-detection pump (LDP) on US-spec cars.
BMW P0455 — EVAP system gross leak on BMW — fuel cap, purge valve and the leak-detection pump (LDP) on US-spec cars. Typical UK independent garage cost: £40–£320.
What actually causes P0455 on a BMW
BMW EVAP systems are sensitive to fuel cap seal condition — that's check one. The canister purge valve (sits on the intake manifold) also fails commonly with age. US-spec BMWs use a leak-detection pump that can fail and trigger P0455, but UK cars use the engine-off natural vacuum test which is less prone to false flags.
BMW engines that log P0455
- All BMW petrol models
- N20, N52, N54, N55, B48 engines particularly
How we diagnose P0455 on a BMW
- Check fuel cap seal condition and tightness
- ISTA: trigger purge valve activation test
- Smoke-test EVAP system from the service port
- Inspect intake manifold purge line for cracks at the valve
- Clear code, drive 2–3 cycles, recheck
The common misdiagnosis to avoid
Don't condemn an expensive EVAP component before testing the fuel cap and purge valve with a scan tool — these solve the majority of BMW P0455 codes.
BMW P0455 repair cost in the UK
Expect £40–£320 including parts and labour at an independent garage. Main-dealer quotes on BMW are usually higher for the same job, and the spread exists because the cheap cause and the expensive cause throw the same code — pay for the diagnosis before you pay for parts.
Bob's workshop tip
BMW purge valves are integrated into a plastic manifold on later N20/B48 — replacement is straightforward but the valve isn't sold separately on some models, you buy the manifold-mounted assembly.
Codes usually seen alongside P0455 on BMW
- P0440
- P0442
- P0496
Symptoms drivers report with P0455
- Engine warning light appears within a mile of filling up — sometimes the cap wasn't clicked shut
- Strong smell of petrol vapour around the car after parking on a hot day
- MPG barely affected — you'll only notice on the fuel receipts over a month
- MOT emissions test passes but the MIL means an MOT visual fail on any car registered 2018+
- Paired codes: P0440 (generic EVAP), P0441 (purge flow), P0446 (vent circuit), P0455 keeps returning
Repairs that clear P0455
- Refit fuel cap
- Inspect hoses
For the generic, all-makes explanation of this code — meaning, every known cause and UK cost bands — see our P0455 guide.
Reading P0455 on a BMW properly
A generic reader will show P0455 and nothing else. What matters is the freeze-frame data stored with it — engine speed, load, coolant temperature and fuel trims at the moment the fault was logged — plus whether any other module on the BMW has logged something at the same time. Codes rarely arrive alone, and the order they were stored in usually points at which one is the cause and which are the consequences.
Clearing P0455 without fixing it
Erasing the code resets the BMW's readiness monitors as well as the light. The fault returns on the next drive cycle if the cause is still there, and in the meantime the incomplete monitors can stop the car passing an emissions check. After a genuine repair, the car is driven until the relevant monitor completes before it is handed back.
Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P0455 is showing on your BMW, bring any scan results with you — we will read the live data ourselves, confirm which cause it actually is, and price the repair before any work starts.