P0455: EVAP System Large Leak Detected
Updated November 12, 2026
The EVAP system's self-test found a large leak, or no vacuum at all. The most common cause is simply a missing or loose gas cap.
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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 missing, loose or damaged gas cap
- A disconnected or split EVAP hose
- A faulty purge or vent valve
- A damaged charcoal canister
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
- Possible fuel smell
- Trouble refueling if the vent valve or canister is blocked
Is it safe to drive?
Usually safe to drive, but fix it to pass emissions and stop fuel vapor escaping.
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).
- Check the gas cap first and tighten it until it clicks.
- Look over the EVAP hoses near the tank and engine for disconnections.
- Test the purge and vent valves; a smoke test confirms large leaks quickly.
- 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 P0455 mean?
P0455 is the generic OBD2 code for "EVAP System Large Leak Detected." The EVAP system's self-test found a large leak, or no vacuum at all. The most common cause is simply a missing or loose gas cap.
Is it safe to drive with P0455?
Usually safe to drive, but fix it to pass emissions and stop fuel vapor escaping.
How do I check P0455 myself?
Read the code and freeze-frame data with an OBD2 scanner, then: Check the gas cap first and tighten it until it clicks. Look over the EVAP hoses near the tank and engine for disconnections. Test the purge and vent valves; a smoke test confirms large leaks quickly.
Related codes
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