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P0440 on a 2022 Subaru Forester

EVAP System Malfunction (Generic)

P0440 on a 2022 Subaru Forester indicates evap system malfunction (generic). It usually stays drivable short-term but should be diagnosed promptly. The most common cause is loose, worn, or wrong-spec fuel cap (typically $15–$60). Confirm the root cause before replacing parts.

Severity: low Safe to drive (short term) Compact SUV 2020-2024 Subaru Forester

Reviewed by MECH AI Editorial · Last verified

What does P0440 mean on a 2022 Subaru Forester?

P0440 is a generic evaporative emission (EVAP) system fault. The EVAP system captures fuel vapors from the tank and routes them through the charcoal canister to be burned by the engine instead of vented into the atmosphere. P0440 is set when the ECM detects that this sealed system has lost its ability to hold pressure or vacuum during a leak test. It is almost always the first sign of a small leak somewhere between the fuel tank and the engine intake.

This guide covers P0440 across the 2020-2024 Subaru Forester generation — the symptoms, causes, and diagnostic steps below apply to every model year from 2020 through 2024.

Is it safe to drive a 2022 Subaru Forester with P0440?

In most cases a 2022 Subaru Forester stays drivable for short trips with P0440 active, but diagnose and repair it promptly. This is a low-severity code — ignoring it can lead to further damage or a failed emissions test.

What are the symptoms of P0440 on a 2022 Subaru Forester?

What causes P0440 on a 2022 Subaru Forester?

Cause Likelihood Estimated repair (USD)
Loose, worn, or wrong-spec fuel cap Always the first thing to check — costs nothing to tighten or replace. Most common $15–$60
Cracked, kinked, or disconnected EVAP hose Common $30–$200
Failed EVAP purge valve (purge solenoid) stuck open or closed Common $80–$300
Failed EVAP canister vent valve / vent solenoid Common $80–$350
Cracked or damaged EVAP charcoal canister Occasional $200–$600
Pinhole leak in fuel filler neck or tank seam Occasional $150–$800
Failed fuel tank pressure sensor Occasional $100–$350

How to diagnose this on a 2022 Subaru Forester

  1. Inspect and re-seat the fuel cap

    Remove the fuel cap and check the rubber gasket for damage, debris, or twisting. Reinstall hand-tight until the cap clicks. Many vehicles require 3+ click stops. Clear the code and drive several drive cycles to allow the EVAP monitor to retest.

    Tools: None

  2. Read mode 6 / EVAP monitor data

    Pull mode 6 test results for the EVAP system. Look at the small-leak, large-leak, and purge flow test IDs. The specific test that failed narrows the diagnosis from "EVAP system" to which subsystem within it.

    Tools: Scan tool with mode 6 support

  3. Smoke-test the EVAP system

    Introduce low-pressure smoke (typically 0.5 psi) into the EVAP service port. Inspect every hose joint, the charcoal canister, the purge and vent solenoids, the filler neck, and the tank top. Smoke escaping anywhere is the leak — repair it and retest.

    Tools: EVAP smoke machine, UV dye and light (optional), Inspection mirror

  4. Bench-test the purge valve and vent valve

    Remove the purge valve and apply 12 V across its terminals. It should click and open. With no voltage, it should hold vacuum. The vent valve operates in reverse — normally open, closes when energized. Either valve stuck the wrong way will set P0440.

    Tools: 12 V test source, Hand vacuum pump

  5. Check the fuel tank pressure sensor reading

    Compare the live tank pressure PID to a known-good vehicle. A reading that does not change when the cap is removed or when the purge valve is commanded indicates either a failed sensor or a blocked hose to it.

    Tools: Scan tool

NHTSA complaints & recalls for the 2022 Subaru Forester

Owner-reported safety complaints and official recalls filed with the U.S. National Highway Traffic Safety Administration for the 2022 Subaru Forester. Use these to gauge how common a problem is on your specific vehicle before you start chasing Subaru Forester diagnostics.

92 owner complaints
8 involved a crash
6 involved a fire
5 reported injuries
  • ENGINE 10
  • VEHICLE SPEED CONTROL 9
  • VISIBILITY/WIPER 20
  • UNKNOWN OR OTHER 17
  • FORWARD COLLISION AVOIDANCE 12

1 active recall

  • POWER TRAIN:AUTOMATIC TRANSMISSION:PARK/NEUTRAL START INTERLOCK SWITCH Nov 2023

    Subaru of America, Inc. is recalling certain model year 2021 Crosstrek, 2022 Forester, 2021-2023 Legacy, and Outback vehicles. An insufficient weld may allow water to enter the inhibitor switch, causing it to fail.…

    NHTSA campaign 23V755000

How do I fix P0440 on a 2022 Subaru Forester?

About the 2020-2024 Subaru Forester

The 2020-2024 Subaru Forester was commonly sold with the following powertrains: 2.5L H4, 2.0L Turbo H4. Common trims include Base, Premium, Sport, Limited, Touring, Wilderness.

P0440 vs the more specific EVAP codes

P0440 is the catch-all. If the ECM can identify the type of failure more specifically, it will set a narrower code: P0442 (small leak), P0455 (large leak), P0446 (vent control), and so on. Older vehicles often set P0440 when newer vehicles would set one of the more specific codes for the same underlying condition.

Why the gas cap is always step one

A loose or damaged gas cap accounts for roughly one-third of all P0440 set events. The cap is the cheapest part to replace and the most common point of failure. Always tighten until you hear 3+ clicks, and replace any cap whose gasket shows cracks or hardening.

How long after a repair until the code clears

The EVAP leak test only runs under specific conditions: cold soak (engine off for several hours), partial fuel tank (typically 25–75 % full), and a specific outside temperature range. After a repair, expect 2–4 drive cycles before the monitor completes and the readiness flag turns “ready.” Clearing the code with a scan tool removes the light immediately, but the monitor must complete naturally before emissions testing will pass.

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