P0456 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 cause is almost always a fuel cap that was not tightened to the full click, a hardened cap rubber seal, or a hairline crack in a vapour line.
DTC/P0456·Volkswagen
P0456 on Volkswagen: Causes, Symptoms and Fix Cost
Quick Answer
Low SeveritySafe to drive (short-term)Volkswagen
P0456 on a Volkswagen 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 cause is almost always a fuel cap that was not tightened to the full click, a hardened cap rubber seal, or a hairline crack in a vapour line.
Repair cost on Volkswagen€12 - €633
What does P0456 mean on a Volkswagen?
Volkswagen Golf
2005-2024The Golf shares EVAP architecture with the rest of the VAG range. The N80 purge valve is the most common P0456 trigger on Mk6, Mk7, and Mk8. On the 1.2 TSI and 1.4 TSI engines, the valve weeps internally rather than sticking, so it tests fine with a multimeter but fails a vacuum hold test. The fuel cap on Mk7+ is integrated with the filler neck and rarely causes leaks.
What causes P0456 on a Volkswagen?
Beyond the generic causes listed on the main P0456 page, these are the Volkswagen-specific patterns we see most often:
Volkswagen GolfN80 purge valve weeping (passes electrical test, fails vacuum hold)
Volkswagen GolfCracked carbon canister housing on Mk6
How to diagnose P0456 on a Volkswagen with OBD2
Follow these steps to pinpoint the root cause of P0456:
- Tighten the fuel cap until you hear three clear 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 the second most common cause of P0456 after 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 bidirectional scan tool 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 seal will not stick open enough to cause P0446, but is loose enough to fail the very small leak threshold
How much does P0456 cost to fix on a Volkswagen? (EUR)
Estimated repair costs on a Volkswagen (Volkswagen parts and labour typically run 15% above the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0456 on Volkswagen
These codes commonly cluster with P0456 on Volkswagen vehicles:
FAQ: P0456 on Volkswagen
How long can I drive with P0456?
Indefinitely from a mechanical safety standpoint. P0456 only affects emissions, not engine operation. However, the check engine light will fail any EU emissions inspection. Plan the repair before your next TÜV, ITV, TA, SKP, or MOT date.
Will P0456 cause my car to fail TÜV or other EU inspections?
Yes. Every EU technical inspection regime fails a vehicle with an active check engine light, regardless of the underlying code. The pre-inspection OBD readiness check will also catch a recently cleared P0456 because the EVAP monitor takes 3 to 5 drive cycles to complete.
Will P0456 affect my fuel economy?
No, not in any measurable way. The leak is smaller than 0.5mm. The amount of fuel vapour escaping is too small to register on your trip computer. If you are also seeing reduced fuel economy, look for another cause like a faulty oxygen sensor or air leak.
Can hot or cold weather trigger P0456?
Yes. The EVAP monitor compares pressure changes in the fuel system to ambient temperature. Sudden cold snaps can shrink rubber seals just enough to leak below the small-leak threshold. Hot weather can vaporise fuel faster than a marginal canister or valve can handle. P0456 codes that appear only in winter are often a stiffening fuel cap seal.
Why does P0456 keep coming back after I tighten the cap?
Three possibilities. First, the cap seal has hardened and tightening alone is not enough - replace the cap. Second, there is a second leak elsewhere in the system that needs a smoke test to find. Third, on some Toyota and Subaru models the EVAP test parameters are sensitive enough that a slightly degraded purge valve seal will set P0456 even with a perfect cap.
Looking for the full P0456 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0456 guideSkanyx · Volkswagen
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