The Quick Answer above is the generic definition. What follows is the model-specific detail for the BMW models that log P0456.
DTC/P0456·BMW
P0456 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Low SeveritySafe to drive (short-term)BMW
P0456 on a BMW means the engine control unit has detected a very small leak in the evaporative emission control system - smaller than 0.020 inches (0.5mm). This is the smallest leak the OBD-II system can detect. The usual causes are a fuel cap that was not tightened to the full click, a hardened cap rubber seal, or a hairline crack in a vapour line.
Typical repair cost, all makes€10 - €550
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BMW 3 Series
2006-2024BMW 3 Series and 1 Series with the DMTL pump (Diagnostic Module Tank Leakage) can throw P0456 when the DMTL pump motor or its filter fails. The pump is mounted near the charcoal canister and is exposed to road debris, and replacement of the whole DMTL module is the usual fix. Check the fuel cap seal as well, since it costs little to rule out.
What causes P0456 on a BMW?
Beyond the generic causes listed on the main P0456 page, these are the patterns noted for BMW models:
BMW 3 SeriesDMTL pump motor or rubber filter failure
BMW 3 SeriesCracked EVAP line near the fuel filler neck
How to diagnose P0456 on a BMW with OBD2
Follow these steps to pinpoint the root cause of P0456:
- Tighten the fuel cap until it clicks. Clear the code and complete three full drive cycles (cold start to full operating temperature, then cool down) before checking if it returns. EVAP monitors only run under specific temperature and fuel-level conditions
- Inspect the fuel cap rubber seal. If the seal is dry, glossy, cracked, or has lost flexibility, replace the cap. A worn seal is another common cause of P0456 alongside a loose cap
- Perform a smoke test on the EVAP system with the fuel cap installed. A very small leak will appear as a faint, slow plume of smoke. Focus on hose connections, the purge and vent valve bodies, and the canister housing
- Use a propane enrichment test on suspect joints. With the engine idling, slowly direct propane near each EVAP component. If the engine RPM rises, propane is entering through a leak
- Command the purge valve closed with a diagnostic tool that supports actuator tests (often manufacturer-level software) and pull vacuum on the EVAP system. The valve should hold vacuum for at least 30 seconds. A slow leak past the valve seat is a common P0456 cause
- Test the vent valve in the same way. The vent valve must seal completely during the EVAP self-test. A weeping vent valve still opens and closes on command, so it sets no vent-control code such as P0446, but it passes enough vapour to exceed the very small leak threshold
How much does P0456 cost to fix on a BMW? (EUR)
Estimated repair costs for P0456 in EUR, compiled across makes. Expect BMW parts and labour towards the upper end of each range.
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Codes related to P0456
These codes are often seen alongside P0456 or point to related issues, on any make:
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See the main P0456 guideSkanyx · BMW
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