P0455 on a Subaru: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

Safe to drive — this is an emissions leak, not an engine problem, but fix it before your next emissions test.

What P0455 means on a Subaru

On a Subaru, P0455 means the engine computer has detected a large leak in the evaporative emission (EVAP) system, so fuel vapors are escaping. On Subarus, a loose or damaged gas cap is the most common cause, though a disconnected EVAP hose or a failing vent valve can also be behind it.

Is P0455 common on Subarus?

P0455 appears on Subarus like the Outback, Forester, Impreza, and Crosstrek, usually as they age. The gas cap is the first thing to check, and a smoke test will find anything more serious.

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

Symptoms

Check engine light is on
Possible fuel smell
No change in performance
Emissions test failure

Common causes

most common: Loose, missing, or damaged gas cap
common: Disconnected or cracked EVAP hose
common: Faulty EVAP purge or vent valve
less common: Crack in the charcoal canister

How to fix it

Fix	DIY?	Typical cost
Tighten or replace the gas cap	Yes	$10–30
Inspect and reconnect or replace cracked EVAP hoses	Yes	$10–60
Have a smoke test performed to find the exact leak	Mechanic	$50–150
Replace a faulty purge or vent valve	Yes	$30–120