P0442 on a 2018 Ford F 150 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 150 Supercab
Ranked from 1,835 NHTSA owner complaints filed for this vehicle.
- 1
Faulty seal/hinge on the capless fuel filler door
High severityAn owner on this exact model documented a poor-quality filler-door seal and hinge pin that lets weather elements into the capless fill path — a well-known small-leak source.
Reported in 1 NHTSA complaint - 2
Rodent-damaged or cracked fuel/EVAP line
Medium severityOne owner found a line chewed through by rodents (soy-based coating), requiring line replacement.
Reported in 1 NHTSA complaintParts:fuel/EVAP line - 3
Fuel vapor leak into the cabin
Medium severityAn owner reported recurring gasoline smell in the cabin with heater use, consistent with an EVAP-side leak.
Reported in 1 NHTSA complaint - 4
Loose or damaged gas cap
Low severityThe single most common small-leak trigger; check the seal and click mechanism first.
Common causeParts:gas cap - 5
Purge valve stuck open
Medium severityAllows outside air into the EVAP system during the leak test.
Common causeParts:EVAP purge valve - 6
Charcoal canister crack
Medium severityA cracked canister housing produces a small, steady leak.
Common causeParts:charcoal canister - 7
Rusted or damaged fuel filler neck
Medium severityCorrosion at the filler neck is a common age-related small-leak point.
Common causeParts:fuel filler neck
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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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