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P0442

P0442 on a 2017 Toyota Corolla

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 2017 Toyota Corolla

Ranked from 187 NHTSA owner complaints filed for this vehicle.

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  1. 1

    EVAP charcoal canister fault

    Medium severity

    This owner's check-engine light was tied to a cluster of 17 stored 'emission control failure' codes; on this platform's EVAP system the canister and its valves are the most common root cause of a multi-code emissions cluster.

    Reported in 1 NHTSA complaint
    Parts:charcoal canister
  2. 2

    EVAP purge valve stuck or leaking

    Medium severity

    This owner reported 5 stored 'emissions and fuel' codes the dealer could not immediately diagnose; a stuck purge valve commonly produces multiple simultaneous EVAP-related codes.

    Reported in 1 NHTSA complaint
    Parts:EVAP purge valve
  3. 3

    Loose or worn gas cap seal

    Low severity

    The most common small-leak cause on any vehicle; check first before condemning EVAP components.

    Common cause
    Parts:fuel filler cap
  4. 4

    EVAP vent valve failure

    Medium severity

    A vent valve that fails to seal fully lets outside air bleed into the system during the leak-detection test.

    Common cause
    Parts:EVAP vent valve
  5. 5

    Cracked or deteriorated EVAP hose

    Medium severity

    Age-hardened rubber lines crack and leak vapor slowly, producing a classic small-leak code.

    Common cause
  6. 6

    Corroded fuel filler neck

    Low severity

    Rust perforation at the filler neck creates a small but persistent leak path.

    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

1

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.

2

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.

3

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.

4

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.

5

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