P0456: EVAP system very small leak detected
The seal test on the petrol vapour system finds a tiny leak. It is often the fuel cap seal, a porous hose or a valve not sealing fully.
| Code | P0456 |
|---|---|
| System | Engine and transmission |
| Group | P04xx, Emissions control |
| Type | Generic: it means the same on every make |
| Can you keep driving? | Yes, no rush |
What P0456 means
The ECU checks whether the tank’s vapour circuit holds vacuum for a while. Here it loses it very slowly, which suggests a pinhole-sized leak. It is one of the hardest EVAP codes to track down.
Most common causes
- Worn or cracked fuel cap seal
- Non-original cap or one that does not fit properly
- Porous vapour hose or one with a hairline crack
- Vent or purge valve not sealing completely
- Small leak at the canister or its joints
Symptoms
- Engine warning light on
- No change in how the car drives
- Occasionally a faint smell of petrol
Can you drive with P0456?
Yes, no rush The car runs as normal and there is no immediate risk. It still needs fixing to pass inspection and stop vapour escaping.
Open the bonnetthe in-depth explanation
How to check it
Replacing the fuel cap is the cheapest first step and cures many cases. If it persists, ask the garage for a smoke test, the reliable way to find leaks this small.
How to read and clear P0456 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0456 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P0452 EVAP pressure sensor circuit low
- P0453 EVAP pressure sensor circuit high
- P0454 EVAP system pressure sensor intermittent signal
- P0455 EVAP system large leak detected
- P0457 EVAP system leak: fuel cap loose or missing
- P0458 EVAP purge control valve circuit low
- P0459 EVAP purge control valve circuit high
- P045A The exhaust gas recirculation B control has an electrical fault
- P0400 Exhaust gas recirculation (EGR) flow malfunction
- P0401 Exhaust gas recirculation (EGR) flow insufficient
- P0402 Exhaust gas recirculation (EGR) flow excessive
- P0403 EGR control circuit malfunction
What does code P0456 mean?
The ECU checks whether the tank’s vapour circuit holds vacuum for a while. Here it loses it very slowly, which suggests a pinhole-sized leak. It is one of the hardest EVAP codes to track down.
Can you drive with P0456?
The car runs as normal and there is no immediate risk. It still needs fixing to pass inspection and stop vapour escaping.
How do you clear P0456?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0456 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
