P0457: The gas cap is loose or missing and vapors are escaping
Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off)
The fuel vapor (EVAP) system found a leak, most often a loose or missing gas cap. Tighten the cap until it clicks. If the light stays on after a few days, or you smell strong gas, get it checked.
Stop driving and get help if
- The check engine light is flashing
- The temperature gauge runs high, or you see steam (overheating)
- The car loses power, hesitates badly or stalls
- You smell burning or see smoke
- A brake warning light comes on, or the brakes feel different
Pull over as soon as you can, turn the engine off, and call a tow or roadside help.
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 the fix could involve
From the cheaper fix to the bigger one. Prices depend on your car, your area and the shop, so ask for a written quote that names the part and the labor before you approve it.
- Gas cap replacement
- Fuel filler neck repair
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. Over the next day or two of your usual trips, many vehicles clear this code on their own without a manual reset. If the light stays on after a couple of drive cycles, replace the cap.
Lewis shows pending codes as well as stored ones, so after you tighten or replace the cap you can scan again and see whether the code returns. Get Lewis on the App Store or Google Play.
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.
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