P0440 on a Subaru: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

You can keep driving — this is a general emissions-system fault, not an engine problem — but fix it before your next emissions test.

What P0440 means on a Subaru

On a Subaru, P0440 means the engine computer detected a general problem in the evaporative emission (EVAP) system that captures fuel vapors from the tank. It is the catch-all EVAP code, less specific than the leak-size codes P0442, P0455, and P0456, so it often appears with other EVAP codes. The car keeps running and driving normally.

Is P0440 common on Subarus?

P0440 appears regularly on Subarus, most often starting with a loose gas cap and then, as the car ages, cracked hoses around the purge solenoid or a worn purge valve. The rubber lines under the hood and near the fuel tank dry out over time. It is an emissions concern, not a mechanical failure.

Commonly reported on: Outback, Forester, Impreza, Crosstrek.

Symptoms

Check engine light on
Possible faint fuel smell
No change in how the car drives

Common causes

most common: Loose, missing, or failing gas cap
common: Cracked EVAP hoses near the purge solenoid
common: Faulty purge valve
less common: Leaking fuel filler hose

How to fix it

Fix	DIY?	Typical cost
Tighten or replace the gas cap	Yes	$10–30
Replace cracked EVAP hoses	Yes	$20–80
Smoke test the EVAP system to locate the leak	Mechanic	$50–150
Replace the purge valve	Yes	$50–140