P0451 on a Subaru: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

You can keep driving a Subaru with P0451 — it's an emissions fault, not an engine problem — but fix it before your next emissions test.

What P0451 means on a Subaru

On a Subaru, P0451 means the fuel tank pressure sensor in the EVAP system is reporting a reading outside the expected range. The sensor lets the engine computer monitor fuel vapor pressure in the tank. A bad reading usually turns on the check engine light without affecting how the car drives.

Is P0451 common on Subarus?

P0451 shows up on Subarus as the fuel tank pressure sensor ages, most often on higher-mileage Outbacks and Foresters. The sensor sits near the fuel tank and can be affected by corrosion and rough roads. It is an emissions fault, not a drivability fault.

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

Symptoms

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

Common causes

most common: Faulty fuel tank pressure sensor
common: Corroded or damaged wiring
common: Stuck EVAP vent valve
less common: Cracked or pinched EVAP hose

How to fix it

Fix	DIY?	Typical cost
Inspect the sensor wiring and connector	Yes	$10–50
Replace the fuel tank pressure sensor	Yes	$120–280
Have the EVAP system smoke tested if the code returns	Mechanic	$50–150