P0457: Evaporative Emission System Leak Detected (Fuel Cap Loose/Off)
Updated November 12, 2026
During its EVAP leak test, the computer found a large leak that matches a loose, missing or damaged fuel cap. It often sets right after refueling.
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🔧 Want to check this yourself? An OBD2 scanner reads the code; models with live data also show the sensor readings used in the checks below. See code readers and scanners from $24.99 ↓ · Which scanner do I need?
Common causes
- A fuel cap that wasn't tightened until it clicked
- A cracked or worn fuel cap seal
- A damaged fuel filler neck
- On capless systems, a dirty or damaged filler flap
Code meanings can vary slightly by manufacturer. Use these as a starting point and confirm with your vehicle's service information or a mechanic before replacing parts.
Symptoms
- Check engine light
- Sometimes a 'check fuel cap' message on the dash
- A fuel smell near the filler
- Usually no change in how the car drives
Is it safe to drive?
Safe to drive. Tighten or replace the cap; the light may take several drive cycles to clear by itself.
How to check it with a scanner
- Plug an OBD2 scanner into the port under the dashboard and read all stored codes and the freeze-frame data (the conditions when the code set).
- Remove the cap and inspect the rubber seal for cracks, then reinstall it until it clicks.
- Check the filler neck lip for rust or damage.
- If the code returns with a good cap, have a smoke test done to find the leak.
- After a repair, clear the code and drive normally for a few days to confirm it doesn't come back.
A basic code reader shows the code; scanners with live data let you watch sensor readings, which is what you need for most of the checks above. See OBD2 scanners under $100.
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Questions
What does P0457 mean?
P0457 is the generic OBD2 code for "Evaporative Emission System Leak Detected (Fuel Cap Loose/Off)." During its EVAP leak test, the computer found a large leak that matches a loose, missing or damaged fuel cap. It often sets right after refueling.
Is it safe to drive with P0457?
Safe to drive. Tighten or replace the cap; the light may take several drive cycles to clear by itself.
How do I check P0457 myself?
Read the code and freeze-frame data with an OBD2 scanner, then: Remove the cap and inspect the rubber seal for cracks, then reinstall it until it clicks. Check the filler neck lip for rust or damage. If the code returns with a good cap, have a smoke test done to find the leak.
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