Emissions

P0442 — Small Leak in the Evaporative Emission (EVAP) System

Severity: low Safe to drive

What P0442 means

The EVAP system captures gasoline vapor from the fuel tank in a charcoal canister and later feeds it to the engine through a purge valve to be burned. To make sure it is sealed, the ECM periodically applies vacuum or pressure and watches the fuel tank pressure sensor. P0442 means the system could not hold pressure, indicating a small leak of roughly 0.040 inch (1 mm).

Symptoms

  • Check engine light on
  • Faint fuel smell near the car
  • Slight drop in fuel economy
  • Failed emissions inspection
  • Stronger fuel odor if the leak is bigger

Possible causes

  1. Loose, worn or poorly sealing gas cap
  2. Cracked EVAP hoses or lines, or loose connections
  3. Leaking or stuck purge valve
  4. Faulty vent valve or vent solenoid
  5. Cracked or damaged charcoal canister
  6. Faulty fuel tank pressure sensor or damaged filler neck

How to diagnose

  1. Read codes and freeze frame data, note them, then clear the code
  2. Inspect the gas cap seal and threads, and tighten or replace the cap
  3. Inspect EVAP hoses and lines near the tank, canister and engine bay for cracks and loose fittings
  4. Check fuel tank pressure sensor readings with a scan tool
  5. Command the purge and vent valves with the scan tool and verify they open and seal
  6. Test power, ground and coil resistance on the valves
  7. Run a smoke test of the EVAP system to locate the leak
  8. After repair, clear the code and run the EVAP monitor drive cycle

Common fixes

  • Tighten or replace the gas cap
  • Replace damaged EVAP hoses, lines or fittings
  • Replace the purge or vent valve
  • Replace the charcoal canister
  • Repair or replace a damaged filler neck or pressure sensor

P0442 on different brands

Ford · manuals
On Ford, P0442:00 in the 2024-2025 gasoline OBD monitor strategy means a small EVAP leak (about 0.040 inch) was detected; it reports the monitor result, not a confirmed failed part.

Questions and answers

Can I drive with P0442?

Yes, usually. It does not endanger the engine or safety. Still, fix it soon to avoid extra emissions, wasted fuel and a failed inspection.

Will the check engine light go off after I replace the gas cap?

If the cap was the cause, the light usually goes out after a few successful EVAP self-tests, which can take several days. You can clear the code with a scanner, but the monitor still has to pass again.

How do I find a small EVAP leak?

A smoke test is the most reliable method: harmless smoke is fed into the system and you watch where it escapes. Start with the gas cap and visible hoses.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.