P0442 on a 2019 Hyundai Sonata

P0442 means the EVAP system could not hold pressure or vacuum during a leak test, but the leak is small.

Not your vehicle? See general P0442 info.

Most common causes on the 2019 Hyundai Sonata

Ranked from 154 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Faulty EVAP purge valve stuck/leaking
Medium severity
Dealer diagnostics flagged the purge valve after an EVAP code appeared alongside an unrelated engine replacement; a leaking purge valve produces a small, steady leak the monitor detects.
Reported in 1 NHTSA complaint
Parts:purge valve
2
Corroded/rusted fuel filler neck
Medium severity
The dealer initially attributed the leak to filler-neck rust/corrosion in this case, though a second independent shop later found the filler neck intact -- worth ruling out but not confirmed here.
Reported in 1 NHTSA complaint
Parts:fuel filler neck
3
Loose, worn, or improperly seated gas cap
Low severity
The single most common small-leak trigger; check that the cap clicks fully and inspect its gasket for cracking.
Common cause
Parts:gas cap
4
Cracked or brittle EVAP hose/line
Medium severity
Rubber/plastic EVAP lines dry-rot with age and heat cycling; a smoke test will show the leak point.
Common cause
Parts:EVAP hose
5
Purge valve stuck or leaking
Medium severity
A purge valve that doesn't seal fully allows a small, steady leak into the intake path that the EVAP monitor detects during its leak test.
Common cause
Parts:purge valve
6
Vent valve/solenoid not sealing fully
Medium severity
A vent valve that doesn't close completely prevents the system from holding vacuum/pressure during the self-test.
Common cause
Parts:vent valve
7
Cracked charcoal canister
Medium severity
Canister housings crack from age or road debris impact; a smoke test with the canister isolated will confirm.
Common cause
Parts:EVAP canister
8
Corroded or rusted fuel filler neck
Medium severity
Road salt and moisture rust the filler neck; inspect it and the cap seating surface for pitting.
Common cause
Parts:fuel filler neck
9
Deteriorated O-rings/grommets at EVAP line fittings
Low severity
Hardened seals at quick-connect fittings leak slowly enough to trip a small-leak code but not always be visible without smoke testing.
Common cause

Part links go to Amazon search results for this vehicle. As an Amazon Associate, WrenchConnect earns from qualifying purchases — always confirm fitment for your exact trim and engine before ordering.

These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0442 on your car still needs shop confirmation before any repair.

Common symptoms

Check engine light
Fuel smell near vehicle
Usually drives normally
Hard start after fueling in some cases

What to check before replacing parts

Tighten and inspect the gas cap

Look for: A cap that doesn't click to full tightness, has a visibly cracked or flattened seal, or is simply missing is the single most common cause of a small EVAP leak — rule it out first.

Smoke-test the EVAP system

Look for: Because this is a small leak, expect only a thin wisp of smoke or a faint hiss at one spot (a hose, seam, or valve) rather than an obvious cloud — look closely and take your time.

Check purge valve sealing

Look for: A purge valve that doesn't hold vacuum when commanded closed lets a small amount of air bleed through, which the system reads as a leak during its self-test.

Inspect hoses near the tank and engine bay

Look for: Look for small cracks, soft/collapsed spots, or a hose that has pulled loose slightly at a fitting — any of these can leak just enough to trip a small-leak code without an obvious fuel smell.

Verify vent valve operation

Look for: A vent valve that doesn't seal fully when commanded closed prevents the system from holding vacuum during its self-test, which reads as a small leak even with no physical leak in the hoses.

Rather have a pro handle it? Find a vetted local mechanic.

Matching symptoms

Check Engine Light