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Diagnostic code · Emissions / EVAP

Honda P0457 Code: EVAP Leak (Loose Fuel Cap) — Fix

Updated October 8, 2026Sources

On this page 4 sections
Meaning
An EVAP leak traced specifically to the fuel cap — loose, missing, or not sealing.
Checks to start with
Tighten the cap until it clicks; replace it if the seal is worn.
Safe to drive?
If the light is steady, Honda says to avoid high speeds and have the vehicle inspected immediately. If it starts flashing, stop safely. It also won't pass emissions.

P0457 is the EVAP code that points straight at the gas cap. Re-seat the cap until it clicks at least once and drive for several days — the code can clear on its own once the system re-tests. If it doesn't, the leak may not be the cap.

What P0457 means

P0457 stands for “Evaporative Emission System Leak Detected (Fuel Cap Loose/Off).” Of all the EVAP codes, this one points most directly at a single part: the gas cap. Your Honda’s EVAP system has to stay sealed to trap fuel vapor, and a cap that wasn’t clicked tight, or whose rubber seal has hardened with age, lets vapor escape and trips P0457 along with the check engine light.

Start by re-seating the cap until it clicks at least once and driving for several days. The code can clear itself once the system confirms a seal. If a properly tightened cap in good condition doesn’t fix it, replace the cap with a genuine Honda or OEM-spec one. For the full walkthrough, see the Honda Check Fuel Cap guide.

If even a new cap doesn’t clear it, the leak may be somewhere other than the cap. Look at the related codes P0455 (large EVAP leak) and P0456 (small EVAP leak), and check the filler-neck sealing surface.

Possible causes

  • Gas cap not tightened until it clicks
  • Worn or cracked gas cap seal (hardens with age)
  • Wrong or low-quality aftermarket cap that won't seal
  • Damaged filler-neck sealing surface or threads
  • Cap left off or loose after fueling

Do these checks first

  1. Remove and re-seat the cap, turning until it clicks at least once, then drive for several days to let the system re-test.
  2. Inspect the cap's rubber seal for cracks or hardening; replace the cap if it looks worn.
  3. Fit a genuine Honda or quality OEM-spec cap, since a cap that isn't made for the filler neck may not seal.
  4. Check the filler neck where the cap seats for dirt, damage, or a deformed lip.

FAQ

What does the P0457 code mean on a Honda?
P0457 means the engine computer detected an evaporative emissions (EVAP) leak traced specifically to the fuel cap — it's loose, missing, worn, or not sealing. It's the most cap-specific of the EVAP leak codes, so the gas cap itself is the first thing to check.
How do I fix a P0457 code on my Honda?
Re-seat the gas cap, turning it until it clicks at least once, then drive normally for several days — the code can clear on its own once the system confirms a good seal. If the cap's rubber seal is cracked or hardened, replace it with a genuine Honda or quality OEM cap.
Is it safe to drive with a P0457 code?
If the check engine light is steady, Honda says to avoid high speeds and have the vehicle inspected immediately. If the light starts flashing, stop safely. With P0457, the system is venting a little fuel vapor, and the car won't pass an emissions test until that's resolved. Tighten or replace the cap.
I tightened the gas cap but the P0457 code is still there — why?
Two reasons: the system can take several days of driving to re-test and clear the code, and if the cap's seal is cracked or hardened it won't seal even when tight. Replace the cap with an OEM-spec one. If the code still won't clear with a new cap, check the filler-neck sealing surface for damage.
What is the difference between P0457 and P0455?
Both are EVAP leaks. P0457 is traced specifically to the fuel cap (loose or missing), while P0455 is a large EVAP leak that may be the cap but can also be a cracked hose or a stuck vent valve. P0456 is a small EVAP leak. With all three, start by checking the cap.

Sources

Owner's manual references are to the model and year named above. Wording and procedures can differ on your Honda, so check your own owner's manual.

How we source and correct →