P0456: Evaporative Emission System Very Small Leak Detected

Symptoms

• Check engine light
• Occasional faint fuel smell
• No driveability symptoms

Common causes

• Loose or aging fuel cap
• Small crack in EVAP hose or canister
• Slightly leaking purge or vent valve
• Worn O-ring at fuel filler neck

What to do?

Replace the fuel cap with an OEM-quality part as a first step - this fixes many P0456 codes. If it returns, the leak is small enough that a smoke test is essentially required to find it. Pay close attention to hose junctions and the area around the charcoal canister.