OBD2 Codes

Nissan P0456 – Meaning, Causes, Symptoms, & Fixes

P0456 evaporative emission control system small leak

Nissan Code P0456 Definition

Evaporative emission control system leak (small).

Nissan Code P0456 Meaning

The evaporative emission control (EVAP) system in your Nissan prevents fuel vapors from escaping into the atmosphere. The fuel vapors from the fuel tank are absorbed and stored by charcoal pellets in the charcoal canister. The vent control valve is controlled by the engine control module (ECM) and allows air to flow into the charcoal canister to purge the gas vapors into the engine air intake to be burned. The flow of the gas vapors from the charcoal canister to the engine air intake is controlled by a purge valve. Both the vent control valve and the purge valve are usually open when the engine is at normal operating temperature. However, the ECM occasionally performs leak tests to ensure the evaporative emission control system is working properly. During the leak test, the ECM closes the vent control valve and purge valve to create a vacuum. If the EVAP system does not maintain the pressure, the ECM recognizes an evaporative emission control leak. In the case of P0456 for your Nissan, it is a small sized leak, smaller than .020" in diameter.

Nissan P0456 Symptoms

  • Check Engine Light is on
  • Decreased fuel economy
  • Fuel smell

Nissan P0456 Causes

  • Loose or damaged gas cap
  • Leaking or disconnected EVAP hose
  • Faulty purge valve
  • Faulty canister vent valve
  • Charcoal canister leak
  • Leaking fuel tank

Nissan Code P0456 Severity – Low

It is unlikely the driver will notice any symptoms with Nissan check engine light code P0456 other than a slight odor of fuel, decreased fuel economy, and the check engine light. However, as with all check engine lights, it is recommended that you get it fixed as soon as possible so the engine can be running at the proper specifications to prevent further damage.

Nissan Code P0456 Common Diagnosis Mistakes

Many assume that a loose fuel cap is the only problem and do not perform all the tests necessary to diagnose the full EVAP system. Make sure to perform the full range of tests in order to properly diagnose the problem.

Nissan Code P0456 Diagnosis Steps

  • Tools Needed to Diagnose:
    • FIXD
    • Digital multimeter

How To Diagnose P0456 For Your Nissan

  1. Scan your Nissan to verify P0456 is the only code present. If other codes are present regarding fuel pressure or the fuel system, repair and diagnose those first.
    1. If it is paired with P0441, P0440, and/or P0446, then there is most likely a solenoid failure, leaking charcoal canister, or a more complex EVAP leak.
  2. Inspect your gas cap to see if it is loose or damaged
    1. If your gas cap is loose, tighten it and clear the code.
    2. Inspect your gas cap for physical damage or deterioration. However, it should be noted that damage to the gas cap or deterioration of its components are not always noticeable. If your gas cap was not loose and you do not see any indications of failure, try replacing the gas cap anyways and clearing the codes. Gas caps are relatively inexpensive and are often the fix for code Nissan P0456.
  3. Check for cracked or disconnected EVAP hoses near or connected to engine air box
    1. Replace cracked/disconnected hoses
    2. Clear code
  4. Inspect the fuel tank and charcoal canister for damage and leaks. Replace if necessary.
  5. Check both the charcoal canister vent valve and purge valve for proper operation. These valves can get sticky causing leaks or the internal solenoid can fail and not operate. To test:
    1. Disconnect the valve connector and test that the valve is receiving power with a multimeter
      1. If there is no power, there is most likely a wiring problem or a faulty powertrain control module.
  6. The leak causing Nissan code P0456 is often too small to see. If you have completed all of these diagnostic steps, a smoke test may be necessary. You can purchase a smoke tester from Amazon to do it yourself, or you may want to take it to a shop to find the leak.

FIXD Team

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