Diagnostic code
P0442 Code: Small EVAP System Leak Detected
P0442 means the evaporative emissions system detected a small vapor leak. The vehicle may drive normally, but the fuel vapor system is not sealing tightly enough during the onboard leak test.
Can I drive?
Driving is usually okay if there is no strong fuel smell, but the code should be fixed before an emissions test.
Repair range
$25-$650
Scanner note
Basic OBD-II scanner with live data
Plain-English Meaning
P0442 means the evaporative emissions system detected a small vapor leak. The vehicle may drive normally, but the fuel vapor system is not sealing tightly enough during the onboard leak test.
Common Causes
Symptoms
- Check engine light
- Occasional fuel smell
- Failed emissions readiness
- Usually no performance change
Diagnostic Steps
- 1Check gas cap fit and seal
- 2Inspect EVAP hoses for small cracks
- 3Run a smoke test at low pressure
- 4Test purge valve sealing
- 5Retest after the vehicle completes its EVAP monitor
Confusable And Related Codes
P0455
Compare →P0455 means the fuel vapor system cannot hold pressure or vacuum during its self-test, and the leak appears large. A loose gas cap is a common simple cause, but hoses, valves, and the charcoal canister can also leak.
P0440
Compare →P0440 is a broad EVAP system fault. Instead of identifying a specific leak size or valve circuit, the computer is saying the fuel vapor control system did not pass its expected self-test.
P0446
Compare →P0446 means the EVAP vent control system is not behaving as expected. The vent valve may be stuck, blocked, electrically faulty, or unable to seal the fuel vapor system during testing.
P1450
Compare →P1450 usually means the vehicle cannot relieve fuel tank vacuum as expected during EVAP operation. It is often associated with purge or vent control problems, a restricted vapor path, or a fuel tank pressure reading that does not change nor
FAQ
Is P0442 a small gas cap leak?
It can be. A worn or loose gas cap is one of the easiest first checks.
Can P0442 be hard to find?
Yes. Small vapor leaks often require a smoke test to locate accurately.
Can I ignore P0442?
The car may drive normally, but the code can fail emissions and should be repaired.
This page is educational and is not a substitute for hands-on vehicle diagnosis. Source notes: Code meaning verified against OBD-II reference sources; explanation is original.