OBD codes / P0442
P0442
MinorEvaporative Emission System Leak Detected (Small Leak)
P0442 is the lowest-urgency category — no effect on performance or safety, only emissions. Try a new or properly tightened gas cap first; if the light clears after a few drives, that was it. It will fail an emissions test until fixed.
What this code means
P0442 means the evaporative emission (EVAP) system has a SMALL leak — the system is mostly sealing but can't hold pressure perfectly. Because the leak is small, it can be hard to find by eye; a smoke test is the usual way to locate it. The most common cause is still the gas cap (loose, worn, or a bad seal), followed by a small crack in an EVAP hose or a slightly leaking purge or vent valve. It has no effect on how the car runs — it's purely an emissions and inspection issue.
Symptoms you might notice
- Check-engine light with no change in how the car drives
- Occasionally a faint fuel smell
- Often appears after refueling
- Failed emissions test
What it costs to fix
Typical range: $20–$350 · about ~0.2–1.5 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Gas cap | $10–$35 | ~0–0.2 hrs |
| EVAP hose / seal repair | $10–$80 | ~0.3–1 hrs |
| Purge or vent valve | $20–$120 | ~0.3–1 hrs |
Start with the gas cap — cheapest and a common cause. A small leak often needs a smoke test (a modest shop diagnostic) to pinpoint, after which the actual repair is usually inexpensive.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0442 for my exact vehicle →
Frequently asked
Can I drive with P0442?
Yes — it doesn't affect how the car runs or its safety. The only consequence is failing an emissions test, so drive normally and fix it at your convenience, ideally before inspection.
Will a new gas cap fix P0442?
Often — a worn or loose gas cap is the most common small-leak cause. Replace or fully tighten it and drive a few cycles; the light may clear by itself. If it returns, a smoke test will find the small crack or seal that's leaking.
Why do I need a smoke test for P0442?
A small leak is usually too tiny to see. A smoke test pushes harmless smoke through the sealed system so the leak shows up — the most reliable way to find it without replacing parts by guesswork.
What's the difference between P0442, P0455, and P0456?
They're all EVAP leaks by size: P0455 is a large leak (often a missing/loose cap, easy to find), P0442 is a small leak, and P0456 is a very small leak (usually a smoke test is required). Same system, different leak sizes.
Seeing P0442 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0442 for my vehicleGeneric OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.