P0442: Evaporative Emission System Leak Detected (Small Leak)

What it means

A small leak (typically equivalent to a 0.040 inch / 1.0 mm orifice) has been detected in the EVAP system. By far the most common cause is a fuel cap that is loose, missing, or has a worn seal.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The evaporative emissions system stores fuel vapors and seals them so they can be routed into the engine for burning. P0442 sets when the module's EVAP test detects a small leak, such as a poor fuel-cap seal or a minor hose leak.

Common causes

Most likely first.

1. Fuel cap loose, missing, or worn seal
2. Small crack in EVAP hose
3. Purge valve leaking

Symptoms

• Check engine light on
• Possible smell of fuel near tank or engine bay
• Failed emissions inspection
• Loose-cap warning may appear

How to diagnose it

1. Read freeze-frame data and check whether the vehicle reports a loose-cap warning or other EVAP codes.
2. Inspect the fuel cap for a missing, damaged, or dirty seal, then refit it securely.
3. Look over accessible EVAP hoses and connections for small cracks, splits, or loose fittings.
4. Test the purge valve for leakage when closed using the manufacturer's procedure.
5. If the leak is not visible, use an EVAP smoke test or other manufacturer-approved leak test to locate it.

Common fixes

• Refit the fuel cap securely.
• Replace a fuel cap with a damaged or worn seal.
• Repair or replace a cracked EVAP hose or loose connection.
• Replace a purge valve if testing confirms it leaks when closed.

Can I keep driving?

The vehicle will generally remain drivable because this is an emissions-system leak, but fuel vapors may escape and the vehicle can fail an emissions inspection. If you smell strong fuel or see a fuel leak, stop safely and have it checked promptly.