OBD-II code · Powertrain (generic)
P0456 Evaporative Emission System Leak Detected (Very Small Leak)
A very small leak (typically equivalent to a 0.020 inch / 0.5 mm orifice) has been detected. Smaller threshold than P0442; intermittent and often weather-dependent. Modern OBD-II requires this monitor on most vehicles since model year 2000.
Is it safe to drive with P0456?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyFuel cap seal hardened or worn
- PossiblePurge or vent valve leaking slightly
- PossibleHairline crack in EVAP hose
Symptoms
- Check engine light on
- Possible smell of fuel near tank or engine bay
- Failed emissions inspection
- Loose-cap warning may appear
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.1–3 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Fuel Filler Cap, Evap Canister, Evap Purge Valve, Evap Vent Valve
Related codes
- P0442Evaporative Emission System Leak Detected (Small Leak)
- P0453Evaporative Emission System Pressure Sensor High Input
- P0454EVAP System Pressure Sensor/Switch A Circuit Intermittent
- P0455Evaporative Emission System Leak Detected (Large Leak)
- P0457Evaporative Emission System Leak Detected (Fuel Cap Loose/Off)
- P0458EVAP System Purge Control Valve A Circuit Low
- P0459EVAP System Purge Control Valve A Circuit High
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.