P0456: Evaporative Emissions System - Small Leak Detected

Wondering why the check engine light is on and what is has to do with code P0456?

Your vehicle has a complex evaporative emissions system to prevent fuel vapors from leaking into your environment. An error code P0456 deals with this system and means there is a small leak detected. Learn more about this essential system and find out how do I fix trouble code P0456?

What is the Evaporative Emissions System?

In order to prevent fuel vapors from escaping and increasing your emissions, your vehicle has an evaporative emissions system that traps these vapors in a charcoal filter when your vehicle is resting and diverts them with an intake vacuum into your engine when it’s operating.

In order to protect this important system, your powertrain control module conducts routine tests on the system. A failure to maintain the correct fuel tank pressure results in trouble code P0456. This means that a leak is allowing vapors to escape, either directly from the fuel tank or from related hoses and parts.

What are the Symptoms of P0456?

It’s unlikely that you’ll notice any changes in the normal operation of your vehicle. The first sign of a trouble code P0456 will typically be your Check Engine light. Over time, you may notice a faint smell of gas or a slight decrease in fuel economy.

So, what does the code P0456 mean? These minor symptoms may make it seem like an issue that doesn’t need immediate attention. However, increased emissions can be harmful for the environment, particularly in closed areas. Check the common causes and look for a solution to promptly restore your evaporative emissions system.

What Causes P0456?

Your evaporative emissions system includes your fuel tank, fuel lines, hoses, a filter canister, and a purge valve. Any of these components could have a minor leak, so here is a complete list of areas you need to inspect to identify the cause:

  • Loose or cracked gas cap
  • Small leak in your fuel tank
  • Cut, rotted or missing fuel lines or hoses
  • Cracked charcoal filter
  • Damaged purge solenoid

The easiest way to identify the cause is with a professional smoke machine. First, close the vent solenoid with a scan tool. If this doesn’t completely seal the system and bring back your fuel tank pressure, a smoke machine will help you determine the air leak.

How to Fix P0456

Now that you’ve found the exact point of the leak, it’s time to replace or repair your evaporative emissions system. Don’t pressurize your system with air while you’re checking for a leak, as this could damage your vent solenoid and purge valve. Instead, remove the smoke machine and inspect the area of the leak.

Evaporative emissions system hoses are unlikely to be damaged through normal use, but can begin to rot or crack from extreme weather conditions. Simply replace the broken section of hose, or consider replacing all your hoses if they show signs of wear.

A filter canister or purge solenoid may need to be completely replaced if there’s visible damage or an air leak. Replacing these components is a more costly solution, but a cracked canister or ineffective solenoid won’t allow your system to pressurize.

Finally, one of the most convenient problems is a loose or damaged gas cap. A gas cap seals your fuel tank and allows it to create a pressurized environment. Even if you don’t completely screw on your gas cap it could cause a vapor leak and trigger error code P0456. Inspect and tighten or replace your gas cap and see if it removes your problem code.

These are a few of the most likely sources of an OBD-II scanner error code P0456 problem. Any air leak in the entire system could break the vacuum and cause you to lose pressure, so you need to carefully inspect each area to find the source of the leak.


