What does P0442 mean?
Evaporative Emission Control System — Small Leak Detected
Direct Answer
P0442 means the ECM detected a small leak (less than 0.040 inches in diameter) in the EVAP system — the sealed system that captures fuel vapors from the gas tank and routes them into the engine rather than releasing them into the atmosphere. The most common cause is a loose or faulty gas cap.
Common Symptoms
- ✓Check engine light on (only symptom in most cases)
- ✓Faint fuel smell near the rear of the vehicle (if a hose is cracked)
- ✓Failed emissions test
Common Causes
- 01Loose, damaged, or missing gas cap (most common)
- 02Cracked or disconnected EVAP hose
- 03Faulty purge valve (stuck open or closed)
- 04Failing charcoal canister
- 05Leak in the fuel tank itself (rare)
How to Fix P0442
Check the gas cap first
Remove the gas cap and reinstall it until you hear one or more clicks. Clear the code and drive for two days. If the light does not return, the loose cap was the cause.
Inspect the gas cap for damage
Look at the seal on the inside of the cap. Cracks, deformation, or a missing seal mean the cap needs replacement. A new OEM-spec cap costs $10–$30.
Smoke test the EVAP system
A shop uses a smoke machine to inject smoke into the EVAP system and visually locate leaks in hoses, the canister, or the purge valve. This is the most reliable way to find non-cap leaks.
Inspect EVAP hoses
Follow the vacuum hoses from the charcoal canister to the engine. Look for cracks, loose connections, or deterioration.
Frequently Asked Questions
Will tightening my gas cap fix P0442?
If a loose cap is the cause, yes — but allow the ECM 1–2 complete drive cycles after tightening before the light clears. If you want it cleared immediately, use a scan tool.
Can P0442 cause my car not to start?
No. EVAP codes do not affect starting, idle, or performance. The only symptom is the check engine light and a failed emissions test.
Estimated Repair Cost
$10–$600
Gas cap: $10–$30. EVAP hose: $50–$150. Purge valve: $100–$200. Charcoal canister: $200–$600.
Safe to Drive?
Yes — with caution
Perfectly safe to drive. Fix the leak to pass emissions.
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