Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off)
The P0457 code means the vehicle's onboard diagnostic system has detected: Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off). This is a minor severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- easy
- Estimated cost
- $8-$30 for gas cap
A cracked or loose gas cap causes 60%+ of EVAP codes. This $8 replacement clears P0442, P0455, and P0457 more often than any other repair.
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If a new gas cap does not clear it, the leak is somewhere in the EVAP plumbing. A smoke machine finds the exact leak -- a cracked hose, bad seal, or stuck vent valve -- in minutes instead of guessing at parts.
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Clear the code after the repair. If the light stays off after 50 miles, you just saved $200+ in shop fees.
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Common Symptoms
- Check Engine Light on
- Fuel smell near vehicle
- No drivability issues
Probable Causes (Ranked by Likelihood)
- Gas cap not fully tightened Very High
- Missing gas cap High
- Damaged gas cap seal High
Step-by-Step Diagnostic Procedure
-
Remove and re-install the gas cap, tightening until it clicks.
-
Inspect the gas cap O-ring seal for cracks, tears, or compression set.
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Clear the code and perform two full drive cycles. If the code does not return, the gas cap was the issue.
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If the code returns after replacing the gas cap, proceed with a full EVAP smoke test.
Common Fixes by Vehicle
What techs usually find when diagnosing P0457 on specific vehicles — tap your vehicle for the fix and the exact part:
2006-2020 Honda Civic/Accord 1.5T/2.0L/2.4L easy DIY
P0457 specifically points to a fuel cap issue as the source of the EVAP leak. On Honda vehicles, the cap gasket hardens over time and no longer seals properly. Replace with a Stant 10838 or OE Honda cap. After replacing, clear the code and drive for 2-3 complete drive cycles. Honda TSB 07-007 covers fuel cap-related EVAP codes.
Labor: 5 min2007-2019 Toyota Camry/Corolla 2.5L/1.8L easy (cap) DIY
The fuel cap O-ring on Toyota vehicles dries out and cracks, especially in hot climates. Replace the cap and also inspect the filler neck for dents, rust, or debris that could prevent a proper seal. A damaged filler neck requires replacement (access from under the rear quarter panel). Start with the cap -- it fixes 80% of P0457 cases.
Labor: 5 min (cap), 1-2 hours (filler neck)2010-2020 Subaru Outback/Forester/Impreza 2.5L easy (cap), moderate (grommet) DIY
Subaru P0457 is almost always the gas cap. However, if a new cap does not fix it, check the fuel filler pipe-to-tank rubber grommet for cracks. Subaru TSB 09-69-14R covers EVAP leak diagnosis. The rubber grommet shrinks in cold climates and allows a small leak. Replace the grommet and retest with a smoke machine.
Labor: 5 min (cap), 1 hour (grommet)Frequently Asked Questions
Will P0457 go away on its own after tightening the gas cap?
The Check Engine Light will not go off on its own immediately. The EVAP monitor must run and pass two drive cycles. You can clear the code manually with a scan tool for immediate results.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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