Loose or improperly fitted gas cap. Non-original (non-conforming) gas cap. Small hole or leak in a vapor hose or tube. Other small EVAP leak. Faulty vent O-ring seal. Defective vent valve. Defective purge valve. Defective leak detection pump. Distorted or damaged fuel tank filler neck, a split carbon canister, a fuel tank sending-unit seal, a fuel tank pressure sensor, or loose clamps and hardened O-rings (listed by RepairPal).

Reseat or replace the gas cap (OBD-Codes.com recommends an OEM cap). Replace a cracked vapor hose. Replace a faulty purge or vent valve or leak detection pump.

P0442🌫 Emissions / EVAPUsually OK to drive

P0442: Evaporative Emission (EVAP) System Leak Detected (small leak) (Meaning, Causes, Fixes)

Q: What does P0442 mean?

P0442 means the EVAP system, which stores fuel vapor so it doesn't escape, has a small leak, as small as about 0.04 inch. Start with the gas cap. The EVAP system routes fuel vapor from the tank through hoses to a charcoal canister. Later, a purge valve lets engine vacuum draw those vapors into the engine to be burned. The PCM tests this system for leaks. P0442 means it found a very small one, from a hole as small as 0.04 inch in diameter.

Q: Can I keep driving with P0442?

Usually OK to drive. Generally safe to keep driving: you likely won't notice drivability problems. If you smell fuel, find the leak promptly.

Reviewed 2026-10-21 · Based on 3 cited source(s)

What P0442 means

The EVAP system routes fuel vapor from the tank through hoses to a charcoal canister. Later, a purge valve lets engine vacuum draw those vapors into the engine to be burned. The PCM tests this system for leaks. P0442 means it found a very small one, from a hole as small as 0.04 inch in diameter.

Severity: can I keep driving?

Usually OK to drive

Generally safe to keep driving: you likely won't notice drivability problems. If you smell fuel, find the leak promptly.

Common symptoms

Check engine light on
Usually no drivability problems
Sometimes a fuel odor

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Loose or improperly fitted gas cap
Non-original (non-conforming) gas cap
Small hole or leak in a vapor hose or tube
Other small EVAP leak
Faulty vent O-ring seal
Defective vent valve
Defective purge valve
Defective leak detection pump
Distorted or damaged fuel tank filler neck, a split carbon canister, a fuel tank sending-unit seal, a fuel tank pressure sensor, or loose clamps and hardened O-rings (listed by RepairPal)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Remove and reinstall the gas cap until it clicks, clear the code, and drive for a day to see if it returns.
Inspect the gas cap seal for cracks or damage.
Look over the EVAP hoses you can see (near the tank, canister and engine) for cracks or holes.

Typical fixes

Reseat or replace the gas cap (OBD-Codes.com recommends an OEM cap)
Replace a cracked vapor hose
Replace a faulty purge or vent valve or leak detection pump

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

The code returns after a new cap: a smoke test is the usual way to find small leaks
An advanced scan tool is needed to run the EVAP leak test or check the purge solenoid
Your state's emissions inspection is coming up

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Will the light go off by itself?

It can. The Wisconsin inspection program explains that if the OBD system checks a component three consecutive times and no longer sees the problem, it turns the light off, for example a few days after you tighten a loose gas cap.

Sources

Last reviewed 2026-10-21. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.