P0440 Code: Evaporative Emission Control System Malfunction

🟢 Low severity · drivable

Safe to drive — this is an emissions-system fault, not an engine problem. Fix it before your next emissions test.

What P0440 means

The computer has detected a general problem in the evaporative emission (EVAP) system, which captures fuel vapors from the tank. P0440 is the general-purpose EVAP fault code, less specific than the leak-size codes P0442/P0455/P0456.

Symptoms

Check engine light is on
Possible faint fuel smell
Usually no driving symptoms

Common causes

most common: Loose, missing, or damaged gas cap
common: Faulty EVAP purge or vent valve
common: Cracked or disconnected EVAP hose
less common: Faulty charcoal canister

How to fix it

Fix	DIY?	Typical cost
Tighten or replace the gas cap	Yes	$10–30
Have a smoke test performed to locate the fault	Mechanic	$50–150
Replace a faulty purge or vent valve	Yes	$30–120

Frequently asked questions

Can I drive with a P0440 code?

Yes. It's an emissions fault and won't affect drivability. Fix it before your next emissions inspection.

Is P0440 usually the gas cap?

Very often, yes. Check the gas cap first — it's the cheapest and most common cause.

What's the difference between P0440 and P0442?

P0440 is a general EVAP malfunction, while P0442/P0455/P0456 specifically point to small, large, or very small leaks.

Related codes

P0442 Code: Evaporative Emission Control System Leak Detected (Small Leak)

P0455 Code: Evaporative Emission Control System Leak Detected (Large Leak)

P0456 Code: Evaporative Emission System Leak Detected (Very Small Leak)

P0440 by vehicle brand

Causes and repair costs for P0440 differ between makes. Pick your brand for the specifics.

P0440 on a Toyota

P0440 on a Honda

P0440 on a Ford

P0440 on a Chevy

P0440 on a Nissan

P0440 on a Mercedes-Benz

P0440 on a Volkswagen

P0440 on a Hyundai

P0440 on a Subaru

P0440 on a Mazda

P0440 on a Jeep

P0440 on a Lexus

P0440 on a Volvo

Related guide: How to Reset a Check Engine Light →

Updated 2026-08. This page is informational and not a substitute for professional diagnosis.