P0442: Evaporative Emission System Leak Detected (Small Leak)
Updated November 12, 2026
The evaporative emissions system traps fuel vapor from the tank. P0442 means the system found a small leak during its self-test, on many vehicles about 0.040 inch (1 mm) across.
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🔧 Want to check this yourself? An OBD2 scanner reads the code; models with live data also show the sensor readings used in the checks below. See code readers and scanners from $24.99 ↓ · Which scanner do I need?
Common causes
- A loose, worn or wrong gas cap
- A cracked EVAP hose or fitting
- A faulty purge or vent valve
- A leaking charcoal canister
Code meanings can vary slightly by manufacturer. Use these as a starting point and confirm with your vehicle's service information or a mechanic before replacing parts.
Symptoms
- Check engine light, usually with no driving symptoms
- Sometimes a faint fuel smell
Is it safe to drive?
Generally safe to drive, but it can fail an emissions test and should be fixed.
How to check it with a scanner
- Plug an OBD2 scanner into the port under the dashboard and read all stored codes and the freeze-frame data (the conditions when the code set).
- Start with the gas cap: make sure it clicks tight and the seal isn't cracked.
- Clear the code and see if it returns after a few drive cycles.
- A smoke test of the EVAP system finds small leaks.
- After a repair, clear the code and drive normally for a few days to confirm it doesn't come back.
A basic code reader shows the code; scanners with live data let you watch sensor readings, which is what you need for most of the checks above. See OBD2 scanners under $100.
Code readers and scanners in stock
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Questions
What does P0442 mean?
P0442 is the generic OBD2 code for "Evaporative Emission System Leak Detected (Small Leak)." The evaporative emissions system traps fuel vapor from the tank. P0442 means the system found a small leak during its self-test, on many vehicles about 0.040 inch (1 mm) across.
Is it safe to drive with P0442?
Generally safe to drive, but it can fail an emissions test and should be fixed.
How do I check P0442 myself?
Read the code and freeze-frame data with an OBD2 scanner, then: Start with the gas cap: make sure it clicks tight and the seal isn't cracked. Clear the code and see if it returns after a few drive cycles. A smoke test of the EVAP system finds small leaks.
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