P0442 on a 2018 Ford F 250 Supercab

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 2018 Ford F 250 Supercab

Ranked from 397 NHTSA owner complaints filed for this vehicle.

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1
Stuck or failing EVAP purge valve
Medium severity
A detailed owner complaint explicitly describes a faulty EVAP purge valve sticking, consistent with an intermittent small-leak EVAP fault.
Reported in 1 NHTSA complaint
Parts:EVAP purge valve
2
EVAP canister/vent line contamination from dust ingress
Low severity
The same complaint describes dust entering the EVAP vent line and working into the canister and fuel-sending area over time, which can crack seals and create a small leak path.
Reported in 1 NHTSA complaint
Parts:EVAP canister
3
Aftermarket emissions system deletion/modification
Low severity
One owner discovered the truck's emissions equipment had been deleted by a previous owner; altered or removed EVAP hardware on modified diesel trucks is a common source of persistent small-leak EVAP codes.
Reported in 1 NHTSA complaint
4
Loose or worn fuel filler cap
Low severity
A cap that isn't sealing properly is the single most common trigger for a small EVAP leak code and should be checked first.
Common cause
Parts:fuel cap
5
Cracked or brittle EVAP hoses/lines
Low severity
Age-hardened rubber EVAP lines crack and produce a small, intermittent vapor leak that only shows up under certain drive-cycle conditions.
Common cause
Parts:EVAP hose
6
Rusted or corroded fuel filler neck
Low severity
Corrosion around the filler neck seal area lets a small amount of vapor escape, especially on trucks exposed to road salt.
Common cause

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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.

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Matching symptoms

Check Engine Light