P0455 and P0442: a leak in the EVAP system
The system that captures fuel vapour has a leak. By far the most common cause is a loose, cracked or missing fuel cap, so check that before you assume anything worse.
Can you keep driving?
Yes. This is not a safety problem for driving.
What the code means
EVAP captures vapour from the fuel tank instead of releasing it into the air. P0442 usually indicates a smaller leak, P0455 a larger and more obvious one.
Common causes
- A loose, cracked or missing fuel cap
- A cracked hose in the EVAP system
- A faulty valve or charcoal canister
What to do now
- Take the fuel cap right off and put it back on until it clicks.
- Look for cracks in the seal on the cap.
- Drive a few cycles and see whether the light clears by itself.
What people often get wrong
Paying for diagnosis before checking the cap. It is two seconds of work, and it is the most common cause.
When the car must go to a workshop
If the light stays on after a few days with an intact cap, the leak is somewhere else, and that needs a smoke test.
Read next
- Your check engine light isn't random
- P0401: insufficient EGR flow
- P0300: misfire on more than one cylinder
This page is general information and does not replace a professional assessment. Symbols, codes and behaviour vary between makes. Always check the handbook for your own car.
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