What does P0440 mean?

The EVAP system has a general fault that stops it from working as designed.

Where should I look first for P0440?

Start with the fuel cap, then the EVAP hoses and valves.

Evaporative emission (EVAP)

P0440 — Evaporative Emission System

The ECU found a general fault in the evaporative emission (EVAP) system, which captures fuel vapour from the tank and burns it in the engine instead of releasing it into the air.

Severity: Low

Common causes

Loose, damaged or wrong fuel cap
Leak or crack in EVAP hoses or canister
Faulty purge or vent valve
Faulty fuel tank pressure sensor
Cracked filler neck

Symptoms

Check engine light
Fuel smell near the car
Failed emissions test
Usually no driving symptoms

How to check

Check and tighten the fuel cap; replace it if the seal is worn
Look for damaged EVAP hoses and connections
Test the purge and vent valves with a scan tool
Use a smoke machine to find the leak

Can you keep driving?

Safe to drive. The system affects emissions, not engine operation; repair it at a convenient time.

Frequently asked questions

What does P0440 mean?: The EVAP system has a general fault that stops it from working as designed.
Where should I look first for P0440?: Start with the fuel cap, then the EVAP hoses and valves.

General reference information. It does not replace a diagnosis on your own vehicle. The same code can have different causes depending on make, model year and engine; check the manufacturer's documentation or ask a technician with a scan tool.