P0442: Evaporative Emission System Small Leak Detected
The fuel vapor system has a small leak, roughly the size of a pinhole.
Severity: 1 of 4
Safe to drive in normal conditions. This is an emissions concern. You will probably fail inspection. Fix it when convenient.
Estimate range covers the repairs listed below; see the cost breakdown. A flashing check engine light, a hot temperature gauge, or brakes that feel different mean stop driving and get help.
What P0442 means
During its self test, the computer seals the EVAP system and watches whether pressure or vacuum holds. If it slowly bleeds away, a small leak is flagged.
Small leaks are notoriously hard to find by eye. A smoke test, where harmless vapor is pushed into the system, is the standard method.
Common causes (cheapest likely first)
- Worn gas cap seal. Inexpensive and common.
- Cracked EVAP hose or connector. Brittle lines near the tank or canister.
- Leaking purge or vent valve. Valves that do not fully seal.
- Filler neck rust or seal leak. Common in salted road regions.
Symptoms
- Steady check engine light
- No change in drivability
- Occasional faint fuel smell
DIY difficulty: Moderate
Try a new cap first. Beyond that, a smoke test is the efficient path.
Tools: OBD-II scanner, Gas cap, Smoke tester (shop tool)
Estimated repair cost
This is an estimate, built from typical parts price ranges plus labor hours times an assumed shop rate of $110 to $190 per hour. Actual prices vary by vehicle, region, and shop. Diagnosis fees are often extra.
| Repair | Parts | Labor | Estimate (low / high) |
|---|---|---|---|
| Gas cap | $10 to $35 | 0.0 to 0.1 h | $10 + 0.0 × $110 = $10 $35 + 0.1 × $190 = $54 |
| Smoke test diagnosis | $0 to $0 | 0.5 to 1.0 h | $0 + 0.5 × $110 = $55 $0 + 1.0 × $190 = $190 |
| EVAP hose or valve | $15 to $150 | 0.3 to 1.5 h | $15 + 0.3 × $110 = $48 $150 + 1.5 × $190 = $435 |
| Filler neck | $60 to $250 | 1.0 to 2.5 h | $60 + 1.0 × $110 = $170 $250 + 2.5 × $190 = $725 |
Watch a repair video
How to Find an EVAP Leak (P0440, P0442, P0455, P0456). Third-party video, loads from YouTube (privacy-enhanced mode) only when you press play. Procedures vary by vehicle. Search YouTube for “P0442 fix” videos.
By make
This code works the same way on every make. See brand notes.
Repair manuals
Step-by-step service manuals with torque specs and wiring diagrams:
Haynes manuals Chilton manuals
Affiliate disclosure: links in this box may earn FixOrPark a commission at no extra cost to you.
Related codes
Check for recalls
Before paying for a repair, enter your VIN in the NHTSA recall lookup. Emissions parts may also be covered by a federal emissions warranty; check your warranty booklet.
FAQ
How long until P0442 clears after a fix?
The EVAP test only runs under certain conditions, often after a cold soak and with a partly full tank. It can take several days of normal driving.
Is a smoke test worth paying for?
Usually. It often saves money by finding the exact leak instead of guessing parts.