P0442 — Small EVAP leak detected — leak smaller than a 1.0 mm equivalent hole, caught during pressure test. Often triggered in cold weather after cold fuel fill
What it means
Common causes
- Loose fuel cap after refueling — 60% of cases
- Aged or hardened fuel cap seal
- Micro-crack in EVAP hose — needs smoke machine to find
- Purge valve doesn't fully close — small leak-through
- Cracked canister body — plastic fatigues, worse in hot climates
- Contaminated vent valve — won't seal during test
- Damaged filler neck — after curb impact
How to diagnose
- 01
Read all stored and pending codes with an OBD-II adapter — get the full picture, not just the one code.
- 02
Capture freeze-frame data (RPM, coolant temperature, engine load) at the exact moment the code triggered.
- 03
Inspect the named subsystem with our app's AI explanation — get vehicle-specific causes for your make, model and year.
Common patterns on specific vehicles
- Universal
In 50% of cases P0442 is just a loose fuel cap. Tighten to click, clear the code, drive 2 cycles — often the code doesn't come back.
- Ford Escape / Fusion
On Ford Escape/Fusion, if a new cap doesn't clear P0442, check the EVAP purge pump seal (behind the rear wheel well). Cracks from road salt.
Empirical mechanic observations. Your case may differ — use as a starting hypothesis, not a diagnosis.
Decode P0442 on your actual car
Plug in an OBD-II adapter and get an AI-powered diagnosis tailored to your vehicle make, model and year — in 30 seconds.