P0456 – Evaporative Emission System Leak Detected (very small leak)

By / August 22, 2022

The P0456 OBD2 code tells you there is a small leak somewhere in your evaporative emission control system. While you likely won’t notice any issues when this code activates, it’s not something you should ignore for long. Fixing this problem quickly can prevent further engine damage.

Diagnosing small leaks in your engine can be tricky, making this one of the more potentially frustrating codes to clear. Read on below to find out how to fix this pesky trouble code. 

P0456 Code Definition

P0456 Code Definition (Generic): Evaporative Emission Control System Leak (small)

P0456 Dodge: Evap System Small Leak

P0456 Jeep: Evap System Small Leak

P0456 Ford: EVAP Control System Very Small Leak (0.020″) Detected

P0456 Nissan: (EVAP) system leak detected (tiny leak .02-inch)

P0456 Hyundai: (EVAP) system leak detected (tiny leak .02-inch)

P0456 BMW: EVAP Control System Small Leak Detected

P0456 Subaru: EVAP Control System Leak – Detected (tiny leak)

Here's where you can get a thorough understanding of the P0456 OBD2 code
If you want to learn about the P0456 OBD2 code, this is the right place

What Does P0456 Mean?

The code P0456 generally indicates a leak in your evaporative emission control (EVAP) system, one of the systems in your car that prevents harmful compounds from mixing into your emissions. It uses charcoal pellets to absorb fuel vapors, releasing the vapors into the engine intake.

There are two valves that control airflow through the EVAP system. The vent control valve allows air into the charcoal canister. On the other side, the purge valve lets it out. Both of these valves are open when your car is running.

The engine control module runs periodic checks of the EVAP system during operation. It closes the valves and increases pressure, monitoring it with the fuel tank pressure sensor. If a vacuum is not maintained during this test, the P0456 trouble code will trigger. It specifically indicates there is a small leak, less than 0.2” in diameter. 

What Are The Symptoms Of The P0456 Code?

Your car will not drive any differently when the P0456 code is active. There are some noticeable symptoms, including:

What Are The Causes Of P0456?

A small leak in any of the components or hoses of the EVAP system can cause this trouble code. The most likely causes of the P0456 code are:

  • Leaks in the EVAP hose
  • Damaged or loose gas cap
  • Damaged or leaking fuel tank
  • Faulty valves around the charcoal canister
  • Leaking or faulty charcoal canister

How Serious Is The P0456 Code?

While often not severe on its own, a leak in the EVAP system could contribute to more severe problems down the line. You can drive safely with the OBD2 code active for a short while, but you should diagnose and fix the cause sooner rather than later.

How To Diagnose The P0456 Code?

Digital multimeter
Digital multimeter is one of the best choices for users to diagnose the P0456 error code.

Tools you’ll need:

  1. OBD2 scan tool
  2. Digital multimeter
  3. Hand-held vacuum pump
  4. Smoke machine

Step-By-Step Process:

  1. Scan your vehicle for other trouble codes. If P0440, P0441, or P0446 also come up, repair those first. You likely have a leaking charcoal canister, faulty solenoid, or complicated leak in the EVAP system. 
  2. Check your gas cap, filler neck, and fuel tank for damage. Tighten the gas cap if it’s loose, and replace any components with noticeable damage.
  3. Inspect the EVAP hoses for cracks and other damage. Re-connect any that are loose and replace any with issues. Pay special attention to the hoses connected to the engine air box. 
  4. Use a scan tool to seal the EVAP system by closing the vent solenoid. Check the fuel tank pressure (FTP) sensor. The reading will be consistent if the system is sealing correctly. 
  5. Make sure the vents around the charcoal canister are functioning correctly. Use a multimeter to check if they’re receiving power. If they’re not, the problem is likely an issue with the wiring or the powertrain control module.
  6. If the vents are receiving power, use a vacuum pump to test their operation. Failing this test but passing the multimeter test means either the valves are faulty or you have an internal solenoid failure. 
  7. Use a smoke test to check for leaks in your EVAP and exhaust systems.

Common Mistakes To Avoid While Diagnosing The P0456 Code

This code is very tricky to diagnose correctly. The small size of the leak makes it challenging to find. Follow through with every step of the diagnosis to make sure you’ve repaired all leaks before replacing sensors or other components. 

The leaks reported by P0456 might not be visible to the naked eye. Running a smoke test is highly recommended before replacing anything just to make sure you’re not missing any smaller issues. 

What Should You Do To Fix The Code P0456?

There is a lot of trial and error that goes into fixing trouble code P0456. Locating and fixing every tiny leak in your system can take some time, and not every test will find every leak. It’s especially important to clear the codes and re-scan the car after every repair with this diagnostic code. 

While P0456 is often a leak, it may be a failure of an EVAP system component. Start by repairing the easiest and most affordable potential fixes. Thus, replacing components like the charcoal canister should be considered a last resort. 

  1. Replace the gas cap if you didn’t already, even if there’s no noticeable damage. Deterioration of the gas cap isn’t always visible to the naked eye. A new gas cap is a quick fix that’s relatively cheap and often clears the P0456 code.
  2. Replace any damaged hoses found during steps 3 and 7 of the diagnosis above. Ensure all hoses are tightly attached, even those you didn’t replace.

Read more: P0169 Wrong Fuel Composition Diagnostic Trouble Code Explained

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