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Powertrain fault code

P0456: Evaporative Emission System Leak Detected (Very Small Leak)

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Not dangerous to drive. Start with the cheapest fix: the fuel cap.

What P0456 means

The system that captures fuel vapour from the tank has a leak or a faulty valve.

Common causes

  • Loose or worn fuel cap (very common)
  • Cracked EVAP hose
  • Faulty purge or vent valve

What to check first

  1. Make sure the fuel cap clicks shut and its seal isn't cracked.
  2. Clear the code and see whether it returns after a few drives.
  3. Have a smoke test done if it comes back.

Get P0456 explained for your car: $2.99

  • P0456 explained in full for your make and model: meaning, how urgent, likely causes and what to check, in order.
  • A short personal note from us within 24 hours, or your money back.
  • Your own private report page you can save as a PDF or show your mechanic.

Read your car's codes yourself, free

Plug a cheap ELM327 OBD-II adapter into the port under the dashboard and open the scan tool: Chrome or Edge on a computer with a USB adapter, or Chrome on Android with a Bluetooth LE adapter. It reads and clears codes and shows emissions readiness. It does not work on iPhone.

Open the free scan tool

Need help with P0456?

Tell us your car and what it is doing with P0456. We reply by email with what to check first, in plain words. Free.

Related codes

P0440P0441P0442P0443P0446P0455

General guidance only, not a diagnosis. A qualified mechanic should confirm the cause before you replace parts.