OBD2 Code P0456: What It Means

Figuring out why your Check Engine Light is on means deciphering OBD-II (or “OBD2”) codes, and that can be kind … Continued

Figuring out why your Check Engine Light is on means deciphering OBD-II (or “OBD2”) codes, and that can be kind of annoying. That’s why Car Bibles did it for you! You’re welcome, now let’s get into solving your issue.

OBD2 P0456: What It Means

This code reads as “Evaporative Emissions System Small Leak Detected” meaning there is a small leak in the system that the car uses to control evaporating fuel vapors from the fuel tank. 

This one’s pretty easy to diagnose and remedy; Car Bibles to the swift rescue! 

Likely Symptoms 

Here’s what you may experience due to the P0456 code:

  • Check Engine Light. This will light up and stay lit until the problem is fixed. Remember that a Check Engine Light will fail any emissions test.
  • There often isn’t much else to go on for this one.

Probable Causes

Here’s what could be causing the issue:

  • Gas cap open or isn’t sealing anymore. The gas cap is the main piece for sealing the EVAP system, and might either be disconnected, loose, or worn out.
  • Worn or loose EVAP lines, fuel filler neck tear, clogged purge control valve. These lines might be worn out or loose, the fuel filler near might be worn or loose, or the purge control valve, also known as the canister purge valve, might be clogged or cashed.

What Part Is Potentially Affected?

Usually, all that’s affected is a loose gas cap that needs a tightening-up. At worst, either some old lines need to be replaced, or the purge control valve might need replacement. 

Possible Fixes

Here are the most common fixes to remedy the P0456 code:

  • Make sure your gas cap is tight. Turn it until it’s tight and clicks. It could be that easy!
  • Replace the gas cap. A factory OEM part will probably look and feel the best, but you should be able to pick up a cap that fits at any auto parts store.
  • Smoke test the EVAP system. Smoke testers are cheap and plentiful. Using one will tell you which lines might have miniscule cracks or other types of leaks, just by pumping some harmless, non-flammable smoke into the gas tank.
  • Inspect and replace EVAP lines going from gas tank to the charcoal canister. This one’s pretty easy, though usually means getting under the car on jack stands, potentially with one of the rear wheels removed. Sometimes it’s a loose connection that needs re-tightening, other times it means replacing the entire line. Luckily the lines are sold in bulk and cheap to purchase.
  • Inspect and potentially replace the purge control valve. The purge control valve might be mucked up with dirt and debris, preventing it from properly closing and sealing. If not, it might just need to be replaced. Luckily, like a gas cap, these are also usually cheap to replace.

Finding The Parts You Need

Now that you’ve figured out what’s wrong with your hooptie, let’s talk about where you’re gonna find that part’s replacement.

There are plenty of places you can buy auto parts from, but Car Bibles gets paid if you click this Advance Auto link so that’s the one we’re serving up. Advance Auto Parts also has delivery, curbside pickup, and a host of helpful diagrams to aid your repair!

Peter Nelson
Peter Nelson

Peter Nelson has been wrenching on and playing with cars since he started driving them quickly between the cones at Chicagoland autocross events in his late teens. Nowadays, he can be found wringing out his Mazda2 at tracks all over California. His writing background includes Winding Road, Donut Media, and Autolist.com. He's also an avid cyclist and '80s/'90s action film connoisseur. Contact the author here.