P0457 means the ECU detected an evaporative system leak consistent with a loose, missing, or damaged fuel cap. The code is specifically tuned to flag cap-sized leaks before flagging generic small (P0442) or large (P0455) leaks. The first thing to check is always the cap itself.
DTC/P0457·Audi
P0457 on Audi: Causes, Symptoms and Fix Cost
Quick Answer
Low SeveritySafe to drive (short-term)Audi
P0457 on a Audi means the ECU detected an evaporative system leak consistent with a loose, missing, or damaged fuel cap. The code is specifically tuned to flag cap-sized leaks before flagging generic small (P0442) or large (P0455) leaks. The first thing to check is always the cap itself.
What does P0457 mean on a Audi?
Audi A4
2005–2024B7 and B8 A4 share the bayonet-style cap with the VW Golf. P0457 is one of the most common codes set on these vehicles, almost always due to operator error at the pump. Train all drivers to twist the cap until it audibly clicks at least twice.
What causes P0457 on a Audi?
Beyond the generic causes listed on the main P0457 page, these are the Audi-specific patterns we see most often:
Audi A4Bayonet cap not seated properly at refuelling
Audi A4Worn cap seal at 100,000+ km
How to diagnose P0457 on a Audi with OBD2
Follow these steps to pinpoint the root cause of P0457:
- Remove the fuel cap and inspect the rubber seal for cracks, brittleness, or debris. If the seal compresses unevenly when squeezed, replace the cap
- Re-seat the cap and tighten until you hear at least three clicks. Clear the code and drive for 3 to 5 cycles to let the EVAP monitor retest
- If the code returns with a known good cap, inspect the fuel filler neck. Look for damage to the threads or to the sealing surface where the cap meets the neck
- On capless filler systems (newer Ford, BMW), inspect the flapper assembly for debris, damaged seals, or a stuck flapper. Clean carefully or replace the assembly if damaged
- If the cap and filler neck are good, perform a smoke test focusing on the upper portion of the EVAP system. A leak at the tank top or fuel pump module gasket can mimic a cap leak
How much does P0457 cost to fix on a Audi? (EUR)
Estimated repair costs on a Audi (Audi parts and labour typically run 25% 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 P0457 on Audi
These codes commonly cluster with P0457 on Audi vehicles:
FAQ: P0457 on Audi
How long does P0457 take to clear after I tighten the cap?
After tightening the cap or replacing it, the ECU needs 3 to 5 complete drive cycles to retest the EVAP system and clear the code. A drive cycle includes a cold start, mixed driving over 15 to 20 minutes, and shutdown. You can also clear it manually with a scan tool to confirm the fix immediately.
Is P0457 different from a generic EVAP leak code?
Yes. P0457 is specifically tuned to the leak size associated with a loose or missing fuel cap (typically a medium-size leak). The ECU sets P0457 rather than the generic P0455 (large leak) or P0442 (small leak) when the leak profile matches a cap-sized opening, giving the driver a more specific hint.
Why does my fuel cap warning light keep coming on?
If you've already tightened the cap and the light returns, the rubber seal is most likely worn, cracked, or contaminated with fuel residue. Replacement caps cost 10 to 40 EUR and take seconds to install. Always buy a manufacturer-spec or OEM-equivalent cap, not the cheapest universal option.
Can topping off the fuel tank cause P0457?
Yes, indirectly. Overfilling the tank past the first click of the fuel nozzle can saturate the charcoal canister with liquid fuel. A saturated canister cannot hold vacuum properly during EVAP self-tests and can set leak codes including P0457. The fix is to stop topping off and let the system self-recover over several drive cycles.
Looking for the full P0457 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0457 guideSkanyx · Audi
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