OBD-II Code · Powertrain
P0456
EVAP System — Very Small Leak Detected
Severity
low
Lowest on our scale. Fix it when convenient.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$20–$500
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
EVAP system very small leak — pinhole-level.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
- Often no driveability symptoms
Likely causes
- Aging fuel cap sealMost common
- Tiny hose crack
- Failed purge or vent valve seal
Read the full diagnostic procedureP0456 is a small EVAP leak, defined as a leak equivalent to a 0.020 inch (0.5 mm) orifice or smaller, detected by the same natural-vacuum or pressure…
P0456 is a small EVAP leak, defined as a leak equivalent to a 0.020 inch (0.5 mm) orifice or smaller, detected by the same natural-vacuum or pressure-decay test logic used for P0455 but at a tighter threshold. Because the leak is small, visual inspection is rarely sufficient and a proper smoke test is almost always required.
Cheapest-first
- replace or re-seat the fuel cap (still a real cause for P0456 even though P0455 catches most cap issues), then check the cap sealing surface on the filler neck for rust or debris.
- Next, introduce smoke at low pressure (0.5 to 1.0 psi, ideally under 15 inH2O / 0.5 inHg) and inspect every EVAP joint, hose, and component slowly under good lighting; small leaks often show only as a thin wisp at a hose clamp, purge valve diaphragm, or canister fitting.
- A healthy EVAP system should hold the engine-off natural-vacuum test better than roughly 7 inH2O of vacuum for 30 seconds.
- Pay special attention to the purge valve, canister vent valve, and any service port caps, as a leaky purge-valve diaphragm that does not seal at rest is a very common small-leak source.
- Caveat: P0456 can take several full drive cycles with cold-start, warm-up, and 4 to 8 hour soaks to re-set after repair; do not assume the fix worked just because the code is gone an hour later.
- Confirm with multiple OBD Mode 6 EVAP test passes.
Vehicle-specific patterns2007 to 2013 Honda Civic/CR-V trips P0456 from the canister vent shut valve corroding on the underside of the vehicle, Honda issued service news for…
- 2007to 2013 Honda Civic/CR-V trips P0456 from the canister vent shut valve corroding on the underside of the vehicle, Honda issued service news for vent valve replacement plus a dust cover kit.
- 2005to 2011 Toyota Camry/RAV4 sets P0456 from the purge VSV diaphragm leaking at rest, with Toyota TSB EG002-12 covering updated VSV.
- 2003to 2009 Subaru Forester/Outback sets P0456 from a cracked carbon canister or leaking fuel-tank pressure sensor o-ring (a $5 part on a 2 hour job).
- 2007to 2014 Ford Edge/Lincoln MKX trips P0456 from a leaking fuel-tank-to-canister line grommet at the tank.
Estimated repair$5 to $400.
Look up another code
P0456 — frequently asked
What does a P0456 code mean?
EVAP system very small leak — pinhole-level.
What causes a P0456 code?
Common causes: Aging fuel cap seal; Tiny hose crack; Failed purge or vent valve seal.
What are the symptoms of a P0456 code?
Typical symptoms: Check engine light; Often no driveability symptoms.
Is it safe to drive with a P0456 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $20-$500.
How do I diagnose a P0456 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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