P0442 Code: Evaporative Emission Control System Leak Detected (Small Leak)
The EVAP system, which traps fuel vapors instead of venting them, has a small leak — it cannot quite hold pressure during its self-test.
What this means for driving
Like P0455, this is an emissions-system fault that does not affect engine running or vehicle handling. The practical consequences are a failed emissions test and vapor escaping. It is worth fixing, but it is not a stop-the-car fault.
When in doubt, have a mechanic assess it promptly. If any of the red-flag symptoms below are present, stop driving and arrange a tow rather than risking it.
Important: This page is general information only — not professional mechanical advice and not a diagnosis for your specific vehicle. Fault causes and severity vary by make, model, year, and condition. A qualified mechanic should confirm any diagnosis before you make driving decisions or authorize repairs.
Red-flag symptoms: stop and get help
- Strong fuel smell inside the car
- Visible fuel leak under the vehicle
- Any other warning light appearing alongside it
Symptoms of P0442
- Check-engine light on (often the only symptom)
- Faint fuel smell near the car
- Failed emissions test
Most likely causes, ranked
- Loose or worn fuel cap seal — the most common cause
- Small crack in an EVAP hose
- Purge or vent valve not sealing fully
- Small leak at the charcoal canister or filler neck
How a mechanic diagnoses it
- Fuel cap checked and replaced if its seal is worn — the cheapest fix is tried first.
- Smoke test to find small leaks that are invisible to the eye.
- Purge and vent valves tested for sealing.
Likely fixes
- Replace fuel cap (DIY)
- Smoke-test diagnosis
- Replace EVAP hose
- Replace purge or vent valve
Repair costs vary by vehicle, region and shop. Get a quote from a local mechanic.
Related codes
- P0455: Evaporative Emission Control System Leak Detected (Gross Leak)
- P0171: System Too Lean (Bank 1)
CheckMyCarCode content is general information only and is not a substitute for professional diagnosis. Trouble-code meanings are standardized for generic (P0xxx) codes, but causes, severity, and repairs vary by vehicle. If your car shows a red-flag symptom, stop driving and get professional help.