P0456 code meaning
EVAP System Leak Detected (very small leak)
Powertrain system Generic code P04xx codes Check engine light
What P0456 means
The evaporative emission (EVAP) system stores fuel vapour from the tank in a charcoal canister; a purge valve lets the engine draw it off, and a vent valve opens the canister to fresh air. P0456 reports a very small leak of 0.020 in (0.5 mm), as CARB requires. Ford uses the engine-off natural vacuum test: after switch-off the closed system must build at least about 190 Pa pressure or 125 Pa vacuum, judged statistically. Saab's Bosch ME9 also tests with the engine off for up to 45 minutes; VW and Audi use a leak detection pump. GM reports this leak size as P0442 instead. The code often appears only after many trips and depends on the weather.
P0456 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.2 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P0456
- Check engine light on (possibly a check fuel cap message)
- Possibly fuel smell
- EVAP readiness or emission inspection not passed
Common causes of P0456
- Most likelyFuel cap seal worn or cap not clicked in
- PossiblePurge or vent valve not sealing
- PossiblePorous hoses or O-rings, hairline crack in canister or filler neck
- Less likelyLeak detection pump itself leaking (VW/Audi)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
EVAP systemFuel capEVAP hosesEVAP leak detection pump
What each part of P0456 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 56 | The exact fault in that area. |
What to do next
- Note P0456 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0456
What does P0456 mean?
P0456 means "EVAP System Leak Detected (very small leak)". The evaporative emission (EVAP) system stores fuel vapour from the tank in a charcoal canister; a purge valve lets the engine draw it off, and a vent valve opens the canister to fresh air. It is a generic code, so it means the same on every make.
Is it safe to drive with P0456?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0456 fail an emissions test?
Yes, it can. P0456 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0456 to fix?
Difficulty: medium. A typical repair takes 0.2 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0456 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.