P0442
PowertrainEvaporative Emission Control System Leak Detected (small leak)
There's a small leak somewhere in your evaporative emissions (EVAP) system, petrol vapour is escaping into the atmosphere instead of being captured.
ⓘ Information only. This page provides general educational information about fault code P0442. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0442 mean?
P0442 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Evaporative Emission Control System Leak Detected (small leak).
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light, usually the only symptom
- • Sometimes a slight smell of petrol around the vehicle
- • Drivability is unaffected
Possible causes
Causes commonly associated with P0442, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Loose, missing, or faulty fuel cap (the most common cause by far)
- 2. Cracked or perished EVAP system hose
- 3. Faulty EVAP purge valve or vent valve
- 4. Damaged charcoal canister
- 5. Faulty fuel tank pressure sensor
- 6. Pinhole leak in the fuel filler neck
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Check the fuel cap is tight, undamaged, and properly seated. Many P0442 codes resolve themselves after the cap is correctly fitted and a few drive cycles complete
- 2. If the cap is sound, inspect the EVAP hoses around the engine bay for cracks
- 3. A workshop smoke test of the EVAP system will pinpoint the leak source
- 4. Test the EVAP purge and vent valves with a diagnostic tool
Common questions about P0442
Can I drive with P0442? +
Yes. It doesn't affect engine performance or safety. It will, however, fail an MOT because the warning light is on.
I tightened the fuel cap, why is the light still on? +
EVAP codes need several drive cycles (typically 10-20) before the system re-tests and clears the code. If the cap was the cause, it should clear itself within a week of normal driving.
Does this code mean my fuel tank is leaking? +
P0442 specifically means a small leak, about the size of a 1mm pinhole. A leaking fuel tank would generally trigger a more serious code and produce visible fuel under the car.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →