P0440

EVAP System

Q: Is it safe to drive with P0440?

Yes. It affects fuel-vapor containment and emissions, not how the car runs — but you'll fail an emissions test until it's fixed.

Q: Can I just clear P0440?

Tighten or replace the cap first, then clear it. If a hose, canister, or valve is leaking, the code returns until that's repaired.

Evaporative emissions (EVAP) Generic OBD-II Low

What it means

P0440 is a general evaporative emission (EVAP) system fault — the system that captures fuel vapors from the tank and routes them to the engine to burn instead of venting them to the air. It typically points to a leak or a faulty component, most often a loose or worn gas cap. The car drives normally; the concern is emissions and vapor loss.

Low

Can I keep driving? Yes — the car drives normally; this is a fuel-vapor containment and emissions issue only.

Real-world scan data

Seen in

261

scans in the past year

Found in

<0.1%

of scans

0.1%

of scans that found faults

Appears alongside · share of P0440 scans

P0456in 36.8% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Occasional smell of fuel vapor near the vehicle
Failed emissions test
Slightly reduced fuel economy

Common causes

Most likely first

Loose, worn, or faulty gas cap (most common)Likely
Leaking or cracked EVAP hoseCommon
Faulty or cracked charcoal canisterCommon
Malfunctioning purge valveLess often
Faulty fuel tank pressure sensorLess often

How to diagnose & fix

Work through it in order

Check and reseat the gas cap; replace it if the seal is worn or cracked.
Drive several complete cycles and see whether the code clears.
Inspect the EVAP hoses and charcoal canister for cracks or leaks.
Have the EVAP system smoke-tested to pinpoint the leak.
Test the purge and vent valves, and the tank pressure sensor, replacing as found. Clear and re-test.

FAQ

Quick answers

Is it safe to drive with P0440?+

Yes. It affects fuel-vapor containment and emissions, not how the car runs — but you'll fail an emissions test until it's fixed.

Can I just clear P0440?+

Tighten or replace the cap first, then clear it. If a hose, canister, or valve is leaking, the code returns until that's repaired.

Read & clear P0440 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX