Repair cost
$90–$650
DIY from $5
DIY difficulty
Easy
If you do it yourself
Urgency
Within a month
Before bigger damage
Common symptoms
- Check engine light on
- Possible fuel odor
- No effect on drivability
- Emissions test failure
Common causes, ranked by likelihood
Based on typical diagnoses for P0455. Work from the most likely cause down before replacing expensive parts.
Loose or missing gas cap 50%
Disconnected or split EVAP hose 25%
Stuck-open vent or purge valve 20%
Damaged charcoal canister 5%
How to diagnose it
- Tighten or replace the gas cap, then clear the code and complete a few drive cycles.
- Look for an obviously disconnected or cracked EVAP hose, which causes large leaks.
- Test the vent valve — if it's stuck open, the system can't seal.
- Smoke-test the system if the leak isn't obvious.
DIY vs shop cost
Shop
$90–$650
Parts + labour at an independent shop.
DIY can save up to $10
Make-specific notes
Chevrolet
A stuck-open vent solenoid is a common large-leak cause on GM vehicles when the gas cap checks out.
P0455 questions, answered
What's the difference between P0455 and P0456?
P0455 is a large EVAP leak — often the gas cap or a disconnected hose. P0456 is a very small leak, like a tiny crack or a worn cap seal, which is harder to find.
Can I drive with P0455?
Yes, it's safe. It's an emissions issue, so fix it to pass testing and avoid wasting fuel vapor, but it won't harm the car to drive in the meantime.