P0442 P0xxx · Powertrain (P) Low severity
Evaporative Emission Control System Leak Detected (Small Leak)
A small leak — typically equivalent to a 0.5–1 mm hole. Harder to find than a gross leak, and the smoke machine is the only realistic tool.
Severity guidance: Low — usually no drivability impact, fix at the next service
Symptoms you will notice
- Faint fuel smell
- Check-engine light
- Failed emissions test
Common causes
Ordered from most to least likely — start at the top.
- 1 Perished vapour hose
- 2 Loose or worn fuel cap seal
- 3 Cracked charcoal canister
- 4 Corroded tank vent line
How to diagnose it
Cheapest and least invasive first — most of these codes are not a parts problem.
- ✓ Replace or re-seat the fuel cap and re-run the monitor if you can.
- ✓ Smoke-test at low pressure and watch for the thinnest wisp.
- ✓ Inspect the canister and all hose ends under the vehicle.
- ✓ Check the filler neck seal and vent line for rust.
Repair options
- Replace the leaking hose
- Replace the fuel cap
- Replace the charcoal canister
P0442 — frequently asked questions
Why is a small leak harder than a big one? +
The leak is near the monitor's threshold, so visual inspection almost never finds it. Smoke is the reliable method.
Can I ignore it? +
It will not strand you, but it fails inspection and wastes fuel vapour. Fix it when convenient.
Confirm the diagnosis before you buy parts
Send us the code, freeze-frame data and the vehicle — our engineers will tell you what to test first.