P0442: Evaporative Emission System Leak Detected (Small Leak)

What P0442 means

P means powertrain (engine and transmission). The 0 marks a generic code defined by SAE, so the same number means the same thing across makes. The third character, 4, places it in the auxiliary emission controls subsystem; the last two digits identify the specific fault.

The EVAP system traps fuel vapour from the tank in a charcoal canister and later burns it in the engine. The engine computer periodically seals the system and checks whether it holds pressure or vacuum; a leak test failure sets a code sized by how large the leak appears to be.

What “Small Leak” means here

The leak test found a leak in the EVAP system around the size the monitor classes as small (commonly described as around 0.040 inch / 1 mm equivalent). Cracked hoses, a worn cap seal, and leaking purge or vent valves are typical.

What you may notice

Symptoms depend on the vehicle and on how the module responds to the fault. Any of these can accompany P0442:

• Usually no drivability symptom
• Fuel smell near the vehicle
• Failed inspection

Causes to consider

• Loose or damaged gas cap
• Cracked EVAP canister hose
• Purge valve leak

Where to start diagnosing P0442

1. Check the fuel cap first: seal condition, correct cap, and that it clicks fully closed.
2. Inspect EVAP hoses around the canister and filler neck for cracks.
3. A smoke test is the most reliable way to find small EVAP leaks.
4. Check the purge and vent valves seal when closed.

Clear the code only after recording freeze frame data: it shows the engine speed, load and temperature at the moment the fault set, which is often the best clue to reproducing it.

Live data to watch

These standard OBD2 values relate to P0442. Support varies by vehicle; a value your car does not report will simply be missing.

Related codes

Codes from the same evaporative emission (EVAP) system family. If several are stored together, the shared part — wiring, a common reference voltage, or the component itself — is the place to start.

Further reading

• OBD2 readiness monitors explained

Symptoms that lead to P0442

If you have not scanned the car yet, or P0442 is one of several codes stored, these guides start from what the vehicle is actually doing.

• The light came on right after you filled up A check engine light that appears within a drive or two of refuelling points almost exclusively at the evaporative…
• It failed the emissions test There are two quite different ways to fail: the car emitted too much, or the car could not prove it was testing…

Frequently Asked Questions