P0457: OBD-II code P0457 flags an EVAP system leak detected — the EVAP self-test failed to hold pressure/vacuum. Very often caused by a loose or damaged fuel cap.

Symptoms

• Check engine light is on; the engine runs and drives normally with no drivability symptoms.
• You may smell fuel around the vehicle after refuelling or when parked in sun.
• The vehicle will fail an OBD-II emissions test until the EVAP monitor runs clean.

Common causes

• A loose, missing, or damaged fuel cap that doesn't seal the filler neck — the #1 cause of P0457.
• A cracked or damaged EVAP hose between the tank, canister, purge valve, or vent valve.
• A failed seal on the charcoal canister, vent valve, or fuel filler neck check valve.

What to do?

Remove the fuel cap and inspect the seal for cracks or contamination; retighten until it clicks and drive several drive cycles — the code often clears on its own. If it returns, smoke-test the EVAP system and inspect hoses. Replace the cap first (cheap), then chase larger leaks.