P0456: Evaporative Emission System Leak Detected (Very Small Leak)
Key takeaways
- P0456 means the computer's leak test found a very small leak, roughly pinhole size, in the sealed system that holds gasoline vapor.
- It doesn't affect how the car drives, so you can keep driving; a raw fuel smell or a visible drip is a different problem and does need attention.
- Check the gas cap first: tighten it until it clicks, look at the rubber seal, and replace a worn or off-brand cap for $15 to $40.
- If the cap isn't it, a smoke test ($100 to $200) finds the leak before anyone buys a valve, filler neck or canister.
- 163 owner complaints filed with NHTSA mention P0456, and 29 of them are for the Ford Focus.
What P0456 means
The sealed system that traps gasoline vapor from your fuel tank has a tiny leak, often no bigger than a pinhole. Scanners call it “Evaporative Emission System Leak Detected (Very Small Leak).” The EVAP system stores tank vapor in a charcoal canister and lets the engine burn it later instead of venting it to the air. To test it, the computer closes the vent valve to seal the system, then watches pressure or vacuum over time. If it drifts back toward normal faster than a tight system should allow, it sets P0456.
“Very small” is defined by the OBD rules: the system has to catch a leak about 0.020 inch across, roughly half a millimeter. The bigger versions of the same test are P0442 (small leak) and P0455 (large leak).
Is it safe to drive?
Yes. A leak this small doesn’t change how the engine runs, and you can keep driving normally while you sort it out. The real costs of ignoring it are a failed emissions inspection and a check engine light that’s already on, so you won’t notice if a second, more serious code shows up.
The one thing that changes the answer is liquid fuel. P0456 tests for vapor leaks. If you smell raw gasoline around the car or see a drip under the tank, that’s a separate problem and a fire risk; don’t keep driving it, and read car smells like gas.
Causes, ranked
| Cause | How you confirm it | Typical cost (US independent shop, 2026) |
|---|---|---|
| Gas cap loose, worn seal, or a poor-fitting replacement | Code appeared after a fill-up; cracked or flattened rubber seal; cap doesn’t click | $0 to tighten, $15–$40 new |
| Vent valve (canister close valve) sticking or its seal leaking | Smoke test at the canister; valve fails a command test with a scan tool | $120–$350 |
| Purge valve leaking | Valve holds no vacuum when closed; stumble right after refueling | $120–$350 |
| Cracked EVAP hose or loose connection | Smoke test shows smoke at a line or fitting | $100–$300 |
| Rusted filler neck or worn filler neck seal | Rust at the filler pipe; smoke at the fuel door area | $250–$700 |
| Cracked charcoal canister | Smoke test at the canister body; sometimes after overfilling the tank | $300–$800 |
A smoke test adds $100–$200 but saves guessing between those parts. Trucks and cars that need the tank lowered to reach a part sit at the top of the ranges.
What to check first
- Tighten the gas cap until it clicks, and look at its rubber seal for cracks or flattening. If the cap is an off-brand replacement, a factory-quality cap is the cheapest real test. More in loose gas cap check engine light.
- Give it a week. After a cap fix, you can clear the code and drive. The leak test only runs under specific conditions, often after the car sits for several hours with the tank between about a quarter and three-quarters full, so the light can take several days to stay off.
- Stop topping off the tank after the pump clicks. Overfilling can push liquid fuel into the canister.
- Get a smoke test if the code comes back. It finds very small leaks that nobody can see.
- Ask about bulletins. Nissan and Infiniti have a bulletin with EVAP leak information for 2012 and newer vehicles, and one traces P0456 on the NV200 to a vent control valve O-ring. Kia has an engine computer logic update for P0456 on some 2023 Sportage models, and several Volkswagen bulletins cover P0456 and P0442 on the Atlas, Tiguan, Taos, Passat and Arteon.
Owners report it too: 163 complaints filed with NHTSA mention P0456, 29 of them for the Ford Focus, 11 of those for 2018 models. Those are reports, not confirmed causes.
What it costs
The cheap outcome is a tightened or new gas cap, $0–$40. The common outcome once the cap is ruled out is a smoke test plus a vent valve, purge valve or hose, usually $200–$550 all in. The expensive outcome is a filler neck or charcoal canister at up to $800. Paying for a smoke test first is cheaper than replacing valves one at a time until the light stays off.
Related codes
P0456 often shows up with, or after, P0455 and P0442, and with vent valve circuit codes like P0446. A light that goes off and comes back with this code is typical; see check engine light comes on and off.
What owners report to NHTSA
163 complaints filed with NHTSA mention P0456, 134 of them since 2015, across 70 different models. The component owners most often filed it under: fuel/propulsion system.
Most-reported models
| Vehicle | Complaints | Model years reported |
|---|---|---|
| FORD FOCUS | 29 | 2012, 2013, 2014, 2017, 2018 |
| JEEP GRAND CHEROKEE | 10 | 2004, 2014, 2015, 2017, 2018 |
| FORD ESCAPE | 10 | 2010, 2011, 2013, 2017, 2018 |
| FORD EDGE | 10 | 2011, 2012, 2013, 2018, 2019 |
| FORD FUSION | 9 | 2010, 2011, 2019, 2020 |
| MERCEDES-BENZ AMG E55 | 4 | 2004, 2005 |
| FORD MUSTANG | 4 | 2013, 2015, 2016 |
| TOYOTA COROLLA | 3 | 2004, 2005, 2007 |
| MERCEDES-BENZ E350 | 3 | 2006, 2007 |
| VOLKSWAGEN PASSAT | 3 | 2006, 2007, 2015 |
Manufacturer service bulletins that name P0456
701 technical service bulletins and manufacturer communications filed with NHTSA mention P0456, from 24 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- INFINITI INFINITI, bulletin 10183904: 2012 AND NEWER INFINITI VEHICLES; EVAP LEAK DTC P0442, P0455, P0456 INFORMATION This bulletin has been amended. See AMENDMENT HISTORY on the last page. Please discard previous versions of this bulletin.
- NISSAN NISSAN, bulletin 10184003: 2012 AND NEWER NISSAN VEHICLES; EVAP LEAK DTC P0442, P0455, P0456 INFORMATION This bulletin has been amended. See AMENDMENT HISTORY on the last page. Please discard previous versions of this bulletin.
- NISSAN TITAN (2012, 2013, 2014, 2015), bulletin 10208948: EVAP LEAK DTC P0442, P0455, P0456 INFORMATION This bulletin has been amended. See AMENDMENT HISTORY on the last page. Please discard previous versions of this bulletin.
- NISSAN NV200 TAXI (2014, 2015, 2016, 2017), bulletin 10208953: DTC P0456 CAUSED BY EVAP LEAK AT VENT CONTROL VALVE O-RING This bulletin has been amended. See AMENDMENT HISTORY on the last page. Please discard previous versions of this bulletin.
- KIA SPORTAGE (2023), bulletin 10211960: TECHNICAL SERVICE BULLETIN: SERVICE ACTION: ECM LOGIC IMPROVEMENT FOR DTC P0456/P013E (SA498) - This bulletin provides the procedure to update the software logic of the Engine Control Module (ECM) system on some 2023MY S…
- VOLKSWAGEN ATLAS (2020, 2021, 2022, 2023), bulletin 10224851: Customer states rattle noise from the underbody heat shields Customer states MIL-on, fault P0442 and/or P0456 stored in ECM memory Customer states rattle noise under vehicle Customer states MIL-on, fault P0463 stored in …
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.
Frequently asked questions
Can I drive with a P0456 code?
Yes. P0456 is a vapor leak so small that it doesn't change how the engine runs, and it isn't a fire risk by itself. The practical problems are a failed emissions inspection and a check engine light that can hide a new, more serious code. If you smell raw gasoline or see fuel dripping, that's not what P0456 tests for; have it checked right away.
Can a gas cap cause P0456?
Yes, and it's the first thing to check. A cap that wasn't tightened, a cracked or hardened rubber seal, or a cheap replacement cap that doesn't seal perfectly can all leave a gap small enough to set P0456. A new cap costs $15 to $40.
How long does it take for P0456 to clear after fixing it?
Often a week or more. The leak test only runs under certain conditions, usually after the car sits for several hours and with the tank neither nearly empty nor full, and the light goes out only after the test passes on several drives in a row. You can clear the code with a scanner, but that also resets readiness for an emissions test.
What is the difference between P0456, P0442 and P0455?
They're the same test with different leak sizes. P0456 is a very small leak, P0442 a small leak, and P0455 a large leak, such as a missing cap or a disconnected hose. Smaller leaks are harder to find, which is why P0456 usually needs a smoke test if the cap isn't the answer.
References
- NHTSA Office of Defects Investigation — vehicle owner complaint flat files
- NHTSA Office of Defects Investigation — manufacturer communications (service bulletin) flat files
- Cal. Code Regs. tit. 13, § 1968.2 — OBD II requirements, evaporative system monitoring (Cornell LII)
- EPA OBD brochure — Do you drive a 1996 or newer car or light truck? (EPA420-F-02-016, 2021 archive)