P0442 on a BMW: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

You can keep driving — this is an emissions leak, not a mechanical problem — but fix it before your next emissions test.

What P0442 means on a BMW

On a BMW, P0442 means the engine computer detected a small leak in the evaporative emission (EVAP) system that traps fuel vapors from the tank. BMW's engine management monitors tank pressure closely, so even a tiny crack in a hose or a worn valve can turn on the check engine light. The car usually keeps driving and performing normally.

Is P0442 common on BMWs?

P0442 shows up often 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