P0442 on a 2018 Ram 1500

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 1500

Ranked from 644 NHTSA owner complaints filed for this vehicle.

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1
Stuck/faulty fuel tank rollover-vent valve
Medium severity
A widely reported Ram 1500 defect (dealer-referenced TSB) where the tank's rollover/vent valve sticks, trapping vapor pressure so the fuel nozzle repeatedly clicks off and vapor/fuel escapes at the filler — a classic small EVAP leak path.
Reported in 13 NHTSA complaints
Parts:fuel tank vent valve fuel tank
2
Charcoal canister overloaded/saturated with fuel
Low severity
One owner traced the recurring fill problem to the vapor canister/fuel-system design, consistent with a saturated canister no longer holding vacuum properly.
Reported in 1 NHTSA complaint
Parts:charcoal canister
3
Loose or worn gas cap
Low severity
The single most common trigger for a small EVAP leak code; confirm the cap seats and clicks fully before chasing anything else.
Common cause
Parts:fuel cap
4
Cracked or perished EVAP hoses/lines
Medium severity
Heat-cycled rubber/plastic vapor lines between the tank, canister, and purge valve crack with age, producing a small, steady leak.
Common cause
5
Purge valve stuck open
Medium severity
A purge valve that fails to seal introduces a small unmetered air path into the EVAP system even with the engine off.
Common cause
Parts:purge valve
6
Rusted/corroded filler neck
Low severity
Road-salt corrosion on the steel filler neck of trucks this age can pit through and create a small vapor 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.

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

Matching symptoms

Check Engine Light