Subaru Outback P0455
TL;DR
P0455 on the Subaru Outback signals a large EVAP leak. The usual culprit is a loose or worn gas cap; less often a cracked EVAP hose, faulty purge or vent valve, or a leaking canister. Safe to drive, but fix it to clear the light.
Why P0455 shows up on the Subaru Outback
The Outback is a wagon that many owners use for road trips, towing, and outdoor gear hauling, so the EVAP system sees a lot of fuel-tank cycling and temperature swings. P0455 specifically flags a large leak, meaning a big enough gap that the computer cannot build or hold EVAP pressure or vacuum during its self-test. On this model the fix is very often simple, but the same code can also point to aging rubber components after high mileage.
Model-typical causes and rough likelihood
- Loose, missing, or worn gas cap (most common, commonly 40-55%): the cap seal hardens or the cap is not clicked tight after refueling.
- Cracked or disconnected EVAP hoses (often reported): rubber lines near the tank and canister get brittle with age and heat.
- Faulty purge or vent valve (moderate): a valve stuck open reads as a large leak.
- Charcoal canister leak (less common): possible after underbody impact or corrosion.
Owner tips for the Outback
Before anything else, remove the gas cap, wipe the seal, and reinstall it until it clicks several times, then drive a few days and see if the light clears on its own. Always refuel with the engine off. If you recently topped off the tank hard past the first click, that alone can trip P0455. If the light returns, have a shop run an EVAP smoke test to pinpoint the leak instead of guessing at parts.
Typical repair cost
A new OEM-style gas cap is inexpensive. Hose or valve replacement is a moderate labor job. A smoke-test diagnosis is usually a flat shop fee that is money well spent before replacing anything.
Summary
| Code | P0455 |
|---|---|
| Meaning | EVAP system leak detected (large leak) |
| Severity | Low |
| Can I drive? | Yes, safe to drive |
| Most common cause | Loose, missing, or worn gas cap |
| Typical repair cost | $15-$40 (cap) up to $150-$400 (hose/valve) |
Full diagnostics
For the complete step-by-step diagnostic and repair guide, see P0455 — full diagnostics.
Frequently asked questions
Is it safe to drive my Subaru Outback with a P0455 code?
Yes, P0455 on a Subaru Outback is a low-severity emissions code and it is safe to keep driving. It affects the evaporative emissions (EVAP) system that contains fuel vapors, not engine performance, braking, or safety. You may notice a faint fuel odor and the check engine light will stay on until the leak is fixed, but the car will run normally.
What is the most common cause of P0455 on a Subaru Outback?
The most common cause of P0455 on a Subaru Outback is a loose, missing, or worn gas cap that no longer seals the fuel system. Because it flags a large EVAP leak, simply removing the cap, cleaning the seal, and reinstalling it until it clicks fixes many cases. If the code returns, the next suspects are cracked EVAP hoses or a stuck purge or vent valve.
How much does it cost to fix P0455 on a Subaru Outback?
If P0455 on a Subaru Outback is caused by the gas cap, a replacement OEM-style cap typically costs about 15 to 40 USD and you can fit it yourself. If a cracked EVAP hose or a faulty purge or vent valve is to blame, expect roughly 150 to 400 USD including parts and labor. Many shops charge a separate EVAP smoke-test diagnostic fee of around 75 to 150 USD to locate the leak first.
Will P0455 clear itself on a Subaru Outback after I tighten the gas cap?
Often yes. On a Subaru Outback, if the gas cap was the cause, tightening or replacing it and then driving through several drive cycles usually lets the computer re-run its EVAP self-test and turn the check engine light off automatically after a few days. If the light does not clear on its own, you can have the code reset with a scan tool, but the underlying leak must be sealed first or it will return.