P0440 on Subaru: How to Diagnose & Fix
Evaporative Emission Control System Malfunction
1 Subaru model · 1 documented issue · $300-$900 repair
P0440 on Subaru by model: symptoms, diagnosis and fix
Rust-belt GD-chassis WRX models are known for corrosion of the steel fuel filler neck and vent tubes behind the left rear wheel area. As the neck rusts through, owners notice a raw fuel smell, difficulty filling the tank, or EVAP leak codes from the compromised venting system. Subaru issued recalls and service campaigns on related Impreza models in salt-belt states because the corrosion could lead to fuel leakage.
Common Symptoms
- raw fuel smell near left rear of car
- check engine light with EVAP leak code
- difficulty filling fuel tank
- visible rust on filler neck
- fuel seepage after fill-up
How to Fix
Inspect the filler neck and vent pipes by removing the left rear wheel and splash shield, looking for rust perforation, dampness, or fuel staining. Repair usually requires replacing the filler neck assembly and associated hoses/clamps; heavily corroded fasteners may need cutting. After repair, clear EVAP codes and verify the system seals with a smoke test.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Subaru 42066FE100 Fuel Filler Pipe
complete rear filler pipe after corrosion/perforation is confirmed Fitment/availability: 2005-2007 Impreza WRX filler-neck branch; supersedes 42066FE060, confirm VIN and associated hoses/clamps Fitment/availability: ships in 1-3 business…
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Owner tips & cautions
- TipCheck recall eligibility by VIN first, especially for cars originally sold in salt-belt states.
P0440 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0440 mean on a Subaru?
P0440 stands for "Evaporative Emission Control System Malfunction." This code indicates a general malfunction in the Evaporative Emission Control (EVAP) system, which captures fuel vapors from the gas tank and routes them to be burned by the engine instead of escaping into the air. The computer ran a self-test and detected the sealed vapor system isn't holding pressure or vacuum correctly, often signaling a leak somewhere in the system. The most frequent and easiest cause is a loose or faulty gas cap. The car will run normally, but it will fail an emissions test and may smell faintly of fuel. On Subaru it is documented across 1 model: WRX.
What are the most common causes of P0440?
The most common causes of P0440 are: Loose, damaged, or missing gas cap, Cracked or disconnected EVAP hose, Faulty purge valve/solenoid, Faulty vent valve/solenoid, Leaking charcoal canister, Damaged fuel tank filler neck or seal, Faulty leak detection pump or pressure sensor. The specific cause varies by vehicle.
How much does it cost to fix P0440 on a Subaru?
Published repair estimates on Subaru range from $300 to $900 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0440 on a different make?
View P0440 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.