P0442 on a 2018 Ram 2500

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 Ram 2500

Ranked from 2,507 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Restricted or malfunctioning fuel filler neck/vent path
Medium severity
Owner reports the fill neck repeatedly 'backs up' during refueling, a classic sign of a restricted EVAP vent path that also allows a small leak.
Reported in 1 NHTSA complaint
2
Stuck fuel tank pressure/vent valve not relieving properly
Medium severity
Owner reports the fuel tank won't allow pressure to release, triggering the check engine light and refueling problems - consistent with a faulty EVAP vent/pressure control valve.
Reported in 1 NHTSA complaint
3
Loose or worn gas cap seal
Low severity
The most common source of a small EVAP leak; a worn O-ring or improperly seated cap fails the leak-detection test.
Common cause
4
Cracked or aged EVAP hose/line
Medium severity
Small cracks in rubber EVAP lines from heat cycling create a measurable small leak.
Common cause
5
Leaking canister purge valve
Medium severity
A purge valve that doesn't seal fully allows a small, continuous leak path detected during the EVAP monitor test.
Common cause
Parts:purge valve
6
Cracked charcoal canister
Medium severity
A hairline crack in the canister housing is a common small-leak source, especially on trucks exposed to road debris/salt.
Common cause
Parts:charcoal canister
7
Rusted or corroded filler neck
Low severity
Corrosion at the filler neck seal point is a common small-leak source on trucks with age/road exposure.
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.

Rather have a pro handle it? Find a vetted local mechanic.

Matching symptoms

Check Engine Light