OBD-II Code · Emissions
P0442
EVAP System — Small Leak Detected
Severity
low
Lowest on our scale. Fix it when convenient.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$0–$150
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
A small evaporative emissions leak. Most often a gas cap issue — tighten or replace first before anything else.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
- Fuel smell near tank
- Passes emissions but CEL stays on
Likely causes
- Loose or worn gas cap (80% of cases)Most common
- Damaged filler neck
- Cracked EVAP line
- Failed purge solenoid
Read the full diagnostic procedureP0442 is the small-leak code — the EVAP system is leaking somewhere in the range of 0.020 to 0.040 inches equivalent diameter, which is a leak you ca…
P0442 is the small-leak code — the EVAP system is leaking somewhere in the range of 0.020 to 0.040 inches equivalent diameter, which is a leak you cannot hear or feel but the ECU can detect by watching how fast the system loses vacuum during the leak-check phase of a drive cycle. This is the most common EVAP code in the wild because the threshold is tight enough that a tired fuel cap O-ring will trip it, but loose enough that the leak source is usually still findable.
Cheapest first check is the fuel cap
- $5-30, two-minute swap, clears the code on roughly 35-45% of P0442 vehicles.
- If the cap is good, smoke test the system from the service port — the smoke will pool and escape from the actual leak, which on most vehicles is the charcoal canister body, a cracked vent or purge line, a degraded O-ring at the fuel filler neck, or a purge solenoid leaking through.
- Smoke is the 80%-of-causes test; nothing else finds a 0.020-inch leak as reliably or as fast.
Vehicle-specific patternsVehicle-specific tendencies: 2005-2015 Toyota Camry, Corolla, RAV4, and Lexus ES/RX throw P0442 most commonly from the fuel cap (Toyota's cap O-ring…
Vehicle-specific tendencies: 2005-2015 Toyota Camry, Corolla, RAV4, and Lexus ES/RX throw P0442 most commonly from the fuel cap (Toyota's cap O-ring hardens around 80-120k miles) followed by the canister vent solenoid.
- 2003-2010Ford 4.6L vehicles crack their charcoal canisters — the plastic gets brittle from underbody heat and a hairline fracture in the canister body is a textbook P0442; replacement canisters run $150-300.
- 2007-2014GM Silverado/Sierra/Tahoe trucks throw P0442 when the vent solenoid gets dust-packed; the truck won't fully seal during the leak test even though there's no actual leak — clean or replace the solenoid and the code clears.
- 2008-2015VW/Audi LDP failure shows up as P0442 because the pump cannot maintain test pressure.
- 2012+Hyundai/Kia with FTPS issues report false low pressure and trip P0442 even on a sealed system; the FTPS is the fix. Repair range: $5 cap, $40 vent solenoid clean, $150-300 canister, $80-150 FTPS, $300-500 LDP.
Look up another code
P0442 — frequently asked
What does a P0442 code mean?
A small evaporative emissions leak. Most often a gas cap issue — tighten or replace first before anything else.
What causes a P0442 code?
Common causes: Loose or worn gas cap (80% of cases); Damaged filler neck; Cracked EVAP line; Failed purge solenoid.
What are the symptoms of a P0442 code?
Typical symptoms: Check engine light; Fuel smell near tank; Passes emissions but CEL stays on.
Is it safe to drive with a P0442 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $0-$150.
How do I diagnose a P0442 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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