P0446 on a BMW: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

You can drive it, but fix the vent system soon if you notice fuel smells or trouble filling the tank.

What P0446 means on a BMW

On a BMW, P0446 means the vent valve that lets air into the EVAP canister is not working correctly — it may be stuck, clogged, or have a wiring fault. When the vent can't open, pressure builds in the fuel tank and the computer logs the fault. The engine runs normally, so the check engine light is the main sign.

Is P0446 common on BMWs?

P0446 shows up on BMWs like the 3 Series, 5 Series, and X models as the vent valve near the charcoal canister ages. The vent valve and its lines sit under the car, where they can pick up dirt and moisture. A stuck valve is the most common cause, with bad wiring and a plugged vent line close behind.

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

Symptoms

Check engine light on
Faint fuel smell near the rear of the car
Slow fuel filling or nozzle clicks off early
No change in power or drivability

Common causes

most common: Vent valve stuck closed or failing
common: Faulty vent valve wiring or connector
common: Clogged vent line or canister filter
less common: Damaged charcoal canister

How to fix it

Fix	DIY?	Typical cost
Replace the vent valve	Yes	$70–200
Repair vent valve wiring or connector	Yes	$40–100
Have a shop test the vent circuit and replace the valve	Mechanic	$150–380
Replace the charcoal canister assembly	Mechanic	$300–650