P0442 on a 2016 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 2016 Ford F 250 Supercab
Ranked from 287 NHTSA owner complaints filed for this vehicle.
- 1
Rusted/rotted fuel filler neck
High severityOne owner found the filler neck had rotted through, letting fuel run down inside the fenderwell and lighting the fuel-cap warning, a textbook small EVAP leak source.
Reported in 1 NHTSA complaintParts:fuel filler neck - 2
Unshielded fuel tank sending unit or fuel line chafing
High severityOne owner noted the fuel tank sending unit is not guarded from road debris on this platform, spraying fuel onto the exhaust; a slow leak here is enough to fail the small-leak EVAP monitor.
Reported in 1 NHTSA complaint - 3
Fuel line leak in the engine compartment
High severityOne owner smelled diesel fuel and traced it to the engine bay before a fire started, showing a leak point in the fuel supply lines consistent with a small EVAP/fuel leak.
Reported in 1 NHTSA complaintParts:fuel line - 4
Loose or worn fuel filler cap
Low severityThe most common baseline small-leak cause; a cap that seats but doesn't seal fully still fails the tighter P0442 threshold.
Common causeParts:fuel filler cap - 5
Cracked EVAP purge or vent valve
Low severityA small crack or worn seat in either valve lets vapor bleed past even when commanded closed.
Common cause - 6
Cracked charcoal canister
Medium severityAge and underbody road exposure crack the canister housing just enough to fail the small-leak monitor.
Common causeParts:charcoal canister
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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.
Rather have a pro handle it? Find a vetted local mechanic.