P0442 — "Evaporative Emission Control System Leak Detected (Small Leak)" — is one of the most common OBD-II codes. In the majority of cases, the culprit is a loose or faulty gas cap.
Step 1: Check the gas cap first (free)
Remove your gas cap, inspect the rubber seal for cracks, and reinstall it firmly until it clicks. Drive normally for 2–3 drive cycles. If the code was triggered by a loose or worn gas cap, the light will turn off on its own. A new OEM-style gas cap costs $10–$25. This single step resolves P0442 in approximately 40–50% of cases.
Step 2: If the code returns, you need a smoke test
A mechanic uses a smoke machine to pressurize the EVAP system and identify exactly where vapor is escaping. This is the only reliable way to find small leaks in hoses, the canister, or the purge/vent solenoids. Cost: $75–$150.
Common causes beyond the gas cap
- Cracked EVAP hose: $100–$200
- Faulty purge solenoid: $80–$200
- Faulty vent solenoid: $75–$200
- Charcoal canister crack: $150–$400
Is P0442 safe to drive with?
Yes — P0442 is a low-urgency code. The car is completely safe to drive. However, you will fail an emissions test with an active P0442. Fix it within 2–4 weeks. Start with the gas cap — it costs $10 and takes 30 seconds.