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P0456 — Evaporative Emission Control System Leak Detected (Very Small Leak)

informational

What it means

The most sensitive EVAP leak test found a loss of pressure corresponding to an opening of about 0.5 mm (0.020 inch). Because the threshold is so tight, the code is often caused by a slightly worn cap seal, a porous rubber grommet or even a valve that closes a fraction of a second late. There are no driveability symptoms at all; the only consequence is the check engine light and a failed emissions readiness check.

Likely causes (most common first)

  1. Aged or dirty fuel cap seal; cap not tightened to the click
  2. Porous EVAP hose or hardened rubber grommet at the canister
  3. Purge valve seat not sealing completely
  4. Slightly leaking O-ring on the fuel pump module or level sender
  5. Refuelling with the engine running, which corrupts the test result
  6. Faulty fuel tank pressure sensor drifting out of calibration

Can you drive with it?

Yes, drive as usual: this is an emissions-only fault with no effect on the engine.

This is the generic meaning. What about your car?

The same code has different typical culprits on different engines. Tell the AI your make, model and year — it will rank the causes for your exact car and give you a check order.

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