P0440 Code: EVAP System Fault — Causes & Fix
P0440 means a general fault in the evaporative emissions (EVAP) system — fuel vapour is not being contained or purged correctly.
- Applies to
- All OBD-II vehicles (any make or model)
- Est. repair cost
- $20 – $400
- Time to fix
- 30 minutes – 2 hours
What it means
Causes include a loose/faulty fuel cap, a cracked EVAP hose, or a failed purge/vent valve. P0440 is a generic OBD-II powertrain code defined in the SAE J2012 standard, so it applies to virtually any 1996-or-newer petrol car or light truck regardless of make. Fix the underlying fault, then clear the code with an OBD-II scan tool — it will return if the problem isn't resolved.
Symptoms
- Check engine light on
- Possible faint fuel smell
- No drivability effect
How to fix it
- 1
Check the fuel cap and hoses
1. Re-tighten or replace the fuel cap. 2. Inspect EVAP hoses for cracks.
- 2
Test the valves
1. Check the purge and vent valves. 2. Repair, then clear the code.
Frequently asked questions
Can a gas cap cause P0440?
Yes — a loose or worn cap is one of the most common causes. Check it before deeper diagnosis.
Last updated July 19, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.