P0442 on a 2015 Ford Focus

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 2015 Ford Focus

Ranked from 1,022 NHTSA owner complaints filed for this vehicle.

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1
Canister purge valve failure (stuck open/leaking)
High severity
Dominant pattern in this batch: repeated stalling (often right after refueling), rough/surging idle, and P1450/P144A-type EVAP codes traced to a failed canister purge valve; this is the subject of Ford recall 18S32/NHTSA 18V735 on Focus models, and many owners report the same failure recurring even after the recall repair.
Reported in 16 NHTSA complaints
Parts:canister purge valve
2
Warped/deformed plastic EVAP fuel tank
Medium severity
Several complaints describe a heat-warped or deformed plastic fuel tank (inspected as part of the same purge-valve recall) disrupting EVAP system sealing and vapor flow.
Reported in 1 NHTSA complaint
Parts:fuel tank
3
Loose, cracked, or missing gas cap
Low severity
A gas cap that won't seal (worn gasket, cross-threaded, or left off) is the single most common trigger for a small/large EVAP leak code; check cap first.
Common cause
Parts:gas cap
4
Cracked or brittle EVAP vapor/vent lines and hoses
Medium severity
Age- and heat-cracked rubber or plastic EVAP lines under the vehicle or in the engine bay allow vapor to escape; smoke-test to pinpoint.
Common cause
5
Canister vent valve (CVS) failure
Medium severity
A vent valve that won't seat allows the EVAP system to bleed to atmosphere, preventing the system from holding vacuum/pressure during self-test.
Common cause
Parts:canister vent valve
6
Charcoal canister crack or saturation
Medium severity
A cracked canister body or one saturated from repeated overfilling can leak vapor or restrict purge flow.
Common cause
Parts:charcoal canister
7
Corroded or rusted fuel filler neck
Low severity
Rust-through on the filler neck (common in road-salt regions) creates a leak path the EVAP monitor detects as a large leak.
Common cause
Parts: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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Matching symptoms

Check Engine Light