P0440 on a BMW: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

You can keep driving — this is a general emissions-system fault, not a mechanical problem — but fix it before your next emissions test.

What P0440 means on a BMW

On a BMW, P0440 means the engine computer detected a general problem in the evaporative emission (EVAP) system that traps fuel vapors from the tank. It is the catch-all EVAP code, less specific than the leak-size codes P0442, P0455, and P0456, so it often appears with other EVAP codes. The car usually keeps running and performing normally.

Is P0440 common on BMWs?

P0440 shows up on BMWs as the rubber and plastic EVAP lines age and crack, especially the hoses around the purge valve under the hood and the vent lines near the fuel tank. The fuel cap, purge valve, and tank vent valve are the usual suspects on this brand. It is an emissions fault, not a drivability fault.

Commonly reported on: 3 Series, 5 Series, X3, X5.

Symptoms

Check engine light on
Possible faint fuel smell near the rear or engine bay
No change in how the car drives

Common causes

most common: Cracked or brittle EVAP hoses under the hood
common: Loose, missing, or failing gas cap
common: Faulty purge valve
less common: Leaking fuel tank vent valve or charcoal canister line

How to fix it

Fix	DIY?	Typical cost
Tighten or replace the gas cap	Yes	$10–30
Replace cracked EVAP hoses	Yes	$20–80
Smoke test the EVAP system to find the exact leak	Mechanic	$50–150
Replace the purge valve	Yes	$60–150