Will the check engine light turn off by itself after I tighten the cap?

Yes, on most vehicles. The EVAP monitor runs during a normal drive cycle and clears the code once the test passes. It typically takes one to two days of normal driving.

Can any gas cap work, or does it need to be the original?

It must be the correct cap for your vehicle. Caps are pressure-rated. A generic or incorrect cap may not seal to spec and the code will return.

What if the code comes back after replacing the cap?

Inspect the filler neck for cracks or damage. Also check that no other EVAP codes are stored, which would point to a different part of the system.

Codes › P0457

P0457: The gas cap is loose or missing and vapors are escaping

Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off)

Low severityCan you keep driving?

Yes. A loose gas cap is not a safety issue. Tighten the cap firmly until it clicks, then drive a normal cycle. The light should turn off on its own within a day or two.

What it means

P0457 is the code that specifically identifies a loose, improperly seated, or missing gas cap as the source of an EVAP system leak. The computer detected a larger pressure drop than normal during the EVAP self-test, consistent with a missing or very loose cap. Of all the check engine light codes, this is one of the most fixable on your own. That said, if you tighten the cap and the code returns, the cap's rubber seal may be cracked or hardened from age and the cap needs replacing.

Common causes

Gas cap not fully tightenedThe most common cause by far. The cap must click or be turned until it no longer rotates.
Damaged or cracked gas cap sealThe rubber O-ring inside the cap hardens and cracks over years and can no longer seal.
Missing gas capCaps left on the roof of the car at a gas station and driven away are a real thing.
Damaged fuel filler neck or sealLess common. If the cap is new and the code returns, inspect the filler neck for cracks.

What it costs

Gas cap replacement$15 to $50
Fuel filler neck repair$100 to $400

Symptoms

Check engine light on
Fuel smell near the rear of the car
No change in driving performance

What to do next

Remove the gas cap, look at the rubber seal for cracks or hardening, and reinstall firmly until you feel resistance or hear a click. Drive normally for one to two days; many vehicles will clear this code on their own without needing a manual reset. If the light stays on after a couple of drive cycles, replace the cap.

Lewis shows whether the EVAP monitor has completed its run since the cap was tightened, so you know when the system has actually self-tested rather than guessing whether the fix worked. Download Lewis.

Related codes

FAQ

Will the check engine light turn off by itself after I tighten the cap?: Yes, on most vehicles. The EVAP monitor runs during a normal drive cycle and clears the code once the test passes. It typically takes one to two days of normal driving.
Can any gas cap work, or does it need to be the original?: It must be the correct cap for your vehicle. Caps are pressure-rated. A generic or incorrect cap may not seal to spec and the code will return.
What if the code comes back after replacing the cap?: Inspect the filler neck for cracks or damage. Also check that no other EVAP codes are stored, which would point to a different part of the system.