P0442 on a 2018 Ford Focus Rs

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 Focus Rs

Ranked from 743 NHTSA owner complaints filed for this vehicle.

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1
Stuck-open Canister Purge Valve (CPV)
Medium severity
A very large cluster of owners describe the purge valve sticking open (the pattern behind NHTSA recall 18V-735 for the EcoBoost Canister Purge Valve), producing EVAP fault codes (P144A/P1450/P0456), stalling after refueling, and hard restarts -- the dominant, well-documented failure pattern on this platform.
Reported in 13 NHTSA complaints
Parts:canister purge valve
2
Failed EVAP canister/valve assembly requiring repeat recall replacement
Medium severity
One owner had the EVAP canister valve assembly replaced three separate times under Ford's recall for the same stalling/EVAP-fault symptoms, indicating the canister/valve assembly is prone to repeat failure.
Reported in 2 NHTSA complaints
Parts:EVAP canister
3
EVAP purge vapor line obstruction
Low severity
Scan data specifically flagged the EVAP purge vapor line as obstructed and called for replacing the canister purge control valve.
Reported in 1 NHTSA complaint
Parts:EVAP purge line
4
Loose or worn fuel filler cap
Low severity
A cap that isn't sealing properly is the single most common trigger for a small EVAP leak code and should be checked first.
Common cause
Parts:fuel cap
5
Cracked EVAP hoses/lines
Low severity
Age-hardened rubber EVAP lines crack over time and produce a small, intermittent vapor leak.
Common cause
Parts:EVAP hose
6
Charcoal canister cracks
Low severity
A cracked canister housing (distinct from the purge valve itself) lets vapor escape and will trigger a small-leak code.
Common cause
Parts:EVAP canister
7
Rusted filler neck
Low severity
Corrosion around the filler neck seal area lets a small amount of vapor escape.
Common cause

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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.

Matching symptoms

Check Engine Light