P0442 means the engine control unit has detected a small leak in the evaporative emission control system. This system captures fuel vapours from the tank and routes them to the engine to be burned. A small leak allows vapours to escape, increasing hydrocarbon emissions.
DTC/P0442·BMW
P0442 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Low SeveritySafe to drive (short-term)BMW
P0442 on a BMW means the engine control unit has detected a small leak in the evaporative emission control system. This system captures fuel vapours from the tank and routes them to the engine to be burned. A small leak allows vapours to escape, increasing hydrocarbon emissions.
Repair cost on BMW€13 - €585
What does P0442 mean on a BMW?
BMW 3 Series
2006-2024BMW vehicles use a leak detection pump (LDP) to test the EVAP system. A failing LDP can falsely trigger P0442 even when there is no actual leak. The fuel tank vent valve on E90 models is also a known failure point. BMW caps are capless on some newer models.
What causes P0442 on a BMW?
Beyond the generic causes listed on the main P0442 page, these are the BMW-specific patterns we see most often:
BMW 3 SeriesFailing leak detection pump giving false positive
BMW 3 SeriesFuel tank vent valve failure on E90 models
How to diagnose P0442 on a BMW with OBD2
Follow these steps to pinpoint the root cause of P0442:
- Check the fuel cap first. Remove it, inspect the rubber seal for cracks or debris, and re-seat it until it clicks. Clear the code and drive for a few days to see if it returns
- Visually inspect all EVAP hoses from the fuel tank to the charcoal canister and from the canister to the purge valve at the engine. Look for cracks, loose clamps, or disconnections
- Perform a smoke test on the EVAP system by sealing the system and introducing smoke. Watch for smoke escaping at hose connections, the canister, or the fuel tank area
- Test the purge valve and vent valve with a scan tool by commanding them open and closed. A stuck-open purge valve can allow ambient air into the system, mimicking a leak
- If the smoke test reveals no external leaks, inspect the charcoal canister for cracks and the fuel tank for damage, particularly around the fuel pump module seal
How much does P0442 cost to fix on a BMW? (EUR)
Estimated repair costs on a BMW (BMW parts and labour typically run 30% above the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0442 on BMW
These codes commonly cluster with P0442 on BMW vehicles:
FAQ: P0442 on BMW
Can a loose gas cap cause P0442?
Yes. A loose, cracked, or missing fuel cap is the most common cause of P0442. The EVAP system is sealed, and even a slight gap at the cap allows vapours to escape. Always tighten the cap until you hear it click and replace it if the seal is worn.
What is the difference between P0442 and P0455?
Both indicate EVAP system leaks, but P0442 is a small leak (less than about 1mm equivalent orifice) while P0455 is a large leak. Small leaks are often from deteriorated hoses or a worn cap seal. Large leaks suggest a disconnected hose or missing cap.
Will P0442 go away on its own?
If the cause was a loose fuel cap and you tighten it properly, the ECU will eventually clear the code after several successful EVAP system tests during normal driving. This may take 3-5 drive cycles. You can also clear it with a scanner.
Is P0442 serious?
It is not mechanically serious and will not damage your engine or affect performance. However, it means fuel vapours are escaping into the atmosphere, and the check engine light will cause a failed emissions inspection in any EU country.
How does the EVAP system detect a small leak?
Most modern vehicles use either a vacuum-based test or a dedicated leak detection pump. The system seals itself and applies a slight vacuum or pressure, then monitors whether it holds. A small drop indicates a leak, and the ECU sets P0442.
Looking for the full P0442 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0442 guideSkanyx · BMW
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