P0442 on a 2016 Ford Mustang

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 Mustang

Ranked from 367 NHTSA owner complaints filed for this vehicle.

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1
Cracked EVAP fitting/line at the fuel tank
High severity
Multiple 2016 Mustang owners had a cracked EVAP fitting or fuel-tank seam confirmed by dealer inspection (photos, smoke test), producing a fuel-vapor odor and a leak that sets a small/large EVAP code.
Reported in 5 NHTSA complaints
Parts:fuel tank EVAP hose
2
Faulty EVAP purge valve
High severity
Two owners had a stuck/faulty purge (evaporator) valve - one stuck open causing stalls right after fueling, the other replaced it twice - a recognized recurring-failure part on this platform.
Reported in 2 NHTSA complaints
Parts:purge valve
3
Capless fuel filler neck leaking vapor
High severity
One owner's P0456 was traced to vapor escaping the capless filler neck design used on this generation, requiring the entire filler pipe (no separate gas cap exists) to be replaced.
Reported in 1 NHTSA complaint
Parts:fuel filler neck
4
Failed EVAP vent valve / canister vent solenoid
Medium severity
A vent valve that won't seal prevents the system from holding vacuum/pressure during the EVAP self-test.
Common cause
Parts:vent valve
5
Cracked charcoal canister
Medium severity
A physically damaged canister housing leaks vapor directly and is a standard EVAP leak-code cause.
Common cause
Parts:charcoal canister
6
Loose or damaged fuel filler cap/seal (non-capless trim)
Medium severity
On trims with a conventional cap, a worn or improperly seated seal is the most common trigger for an EVAP leak code.
Common cause
Parts:gas cap

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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