P0442 on a 2020 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 2020 Ford F 150 Supercab
Ranked from 506 NHTSA owner complaints filed for this vehicle.
- 1
Cracked or deteriorated EVAP/fuel vapor hose
Medium severityOne owner found a visible gasoline leak from a black hose at the top of the fuel tank -- exactly the kind of line that also carries EVAP vapor and would set a small-leak code.
Reported in 1 NHTSA complaint - 2
Small leak near the filler neck / fuel cap seal
Low severityOne owner smelled fuel vapor after fueling with no visible leak found, consistent with a small leak at the filler neck or cap seal.
Reported in 1 NHTSA complaint - 3
Loose or faulty gas cap
Low severityThe most common small EVAP leak source; confirm the cap clicks fully and check its gasket for cracking.
Common causeParts:fuel filler cap - 4
Purge valve failure
Medium severityA purge valve that won't fully seal leaks vapor past it during the EVAP monitor.
Common causeParts:EVAP purge valve - 5
Charcoal canister crack
Medium severityA cracked canister shell is a small, steady vapor leak source.
Common causeParts:EVAP charcoal canister - 6
Vent valve stuck open
Medium severityA vent valve that doesn't seal allows the system to leak down during the leak-check monitor.
Common causeParts:EVAP vent valve
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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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