Evaporative Emission Control System Leak Detected (Small Leak)
The P0442 code means the vehicle's onboard diagnostic system has detected: Evaporative Emission Control System Leak Detected (Small Leak). This is a minor severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- easy
- Estimated cost
- $5-$30 for gas cap; $30-$80 for purge or vent valve; $150-$600 for charcoal canister (up to ~$1,000 when it is tank-mounted and the tank must be dropped); $300-$1,200 if the leak is in the filler neck or fuel tank
A cracked or loose gas cap causes 60%+ of EVAP codes. This $8 replacement clears P0442, P0455, and P0457 more often than any other repair.
If a new gas cap does not clear it, the leak is somewhere in the EVAP plumbing. A smoke machine finds the exact leak -- a cracked hose, bad seal, or stuck vent valve -- in minutes instead of guessing at parts.
Clear the code after the repair. If the light stays off after 50 miles, you just saved $200+ in shop fees.
Affiliate links — we earn a commission at no extra cost to you.
Common Symptoms
- Check Engine Light on (no drivability issues)
- Faint fuel smell near the vehicle
- May fail emissions inspection
Probable Causes (Ranked by Likelihood)
- Loose, cracked, or missing gas cap Very High
- Damaged or cracked EVAP hose or line High
- Vent valve (vent solenoid) not sealing closed Moderate
- Purge valve stuck open or leaking Moderate
- Cracked charcoal canister Low
- Failed fuel tank pressure sensor Low
Common Fixes by Vehicle
What techs usually find when diagnosing P0442 on specific vehicles — tap your vehicle for the fix and the exact part:
2005-2017 Toyota Camry/Corolla easy DIY
Gas cap is the #1 cause. Replace with OEM-style cap (Stant). If code returns, check the EVAP purge valve (Dorman) and the charcoal canister vent valve. Toyota EVAP systems are sensitive -- even a small crack in a hose will trigger this code. Confirm the exact part for your year and engine with a retailer's fitment lookup or your VIN before ordering - these applications split by engine and build date.
Labor: 5 min (cap), 30 min (purge valve)2009-2018 Dodge Ram 1500 5.7L Hemi easy DIY
Check the EVAP purge solenoid (Mopar) mounted on the intake manifold. These fail commonly on Hemi engines. Also inspect the EVAP line running along the frame rail -- road debris and rust damage the plastic lines. Dorman is the replacement line kit. Confirm the exact part for your year and engine with a retailer's fitment lookup or your VIN before ordering - these applications split by engine and build date.
Labor: 30 min2007-2019 Honda CR-V/Accord 2.4L moderate DIY
The EVAP canister vent shut valve (located near the fuel tank) fails frequently. Honda part 17310-T0A-A11. Access requires removing the rear wheel well liner. Also check the fuel tank pressure sensor for proper readings -- a faulty sensor can mimic a small leak.
Labor: 45 min2010-2020 Ford F-150/Explorer 3.5L moderate DIY
The fuel tank deformation on Ford trucks causes intermittent small leaks. The EVAP hose quick-connect fittings also dry out and crack. Inspect all connections at the charcoal canister. A smoke test is essential for finding these small leaks. Your dealer can confirm whether an open service bulletin or warranty extension applies to your VIN.
Labor: 30 min-1 hourFrequently Asked Questions
Can I drive with P0442?
Yes. A small EVAP leak does not affect engine performance or safety. The only consequences are a lit Check Engine Light, a potential emissions test failure, and a very minor increase in hydrocarbon emissions.
How long does it take for P0442 to clear after fixing a gas cap?
After tightening or replacing the gas cap, clear the code with a scan tool or disconnect the battery. The EVAP monitor needs two or three complete drive cycles to run and confirm the repair.
Mechanics Guide Step-by-step diagnosis, and what most sources get wrong
Step-by-Step Diagnostic Procedure
-
Remove and inspect the fuel cap. Look for a cracked or missing seal. Tighten until you hear a click. Clear the code and drive two full warm-up cycles before rechecking.
-
Inspect all EVAP hoses from the charcoal canister to the intake manifold purge port for cracking, kinks, or disconnection.
-
Test the purge valve with a scan tool by commanding it open and closed. Listen for a clicking sound and verify manifold vacuum drops when opened.
-
Test the vent valve (vent solenoid, near the fuel tank/charcoal canister). It is normally open and must close to seal the system during the leak test: command it closed with a scan tool and confirm the system holds vacuum/pressure. A vent valve that won't seal sets a small-leak code with no visible leak.
-
Perform a smoke test on the EVAP system: plug the vent, pressurize the system, and look for smoke escaping from any fitting.
-
Check the fuel tank pressure sensor reading: it should show slight negative pressure during a cold soak test.
Common Misconceptions / Fact Check
-
Commonly claimedP0442 and P0456 are often described interchangeably, and P0442 is frequently quoted as a "0.020 inch leak."
VerifiedThey are two different thresholds, and the regulation defines both physically rather than by feel: leaks are measured against an O’Keefe Controls precision "Type B" orifice of a stated diameter. P0442 corresponds to the 0.040 inch orifice equivalent; the 0.020 inch equivalent is the tighter test behind P0456. A system can pass the 0.040 test and still fail the 0.020 one, which is exactly why plenty of vehicles show P0456 and never show P0442.
-
Commonly claimedOnce the cap is ruled out, the assumption is that the leak must be somewhere in the lines between the purge valve and the engine.
VerifiedThat stretch is the one place the leak monitor deliberately does not cover. The regulation requires the complete evaporative system be monitored for vapour leaks while explicitly excluding the tubing and connections between the purge valve and the intake manifold. A leak there will not set an evap leak code — it shows up as a vacuum leak, in fuel trim and driveability, so chasing P0442 into that section is chasing it into the one area it cannot have come from.
Sources 3
This page is built from documented references. Verify against your own service info before repair work.
- California Air Resources Board, Title 13 CCR 1968.2 (2006 final regulation order)§(e)(4.2.2) treats purge flow and leak detection as separate malfunction conditions, §(e)(4.2.1) defines the 0.040 and 0.020 inch orifice thresholds, and §(e)(4.1) excludes purge-valve-to-intake tubing from leak monitoring
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
Commonly Affected Vehicles
- Toyota Camry and Corolla (2002-2015)
- Honda Civic and Accord
- Chevrolet Silverado and Tahoe
- Ford F-150 and Explorer
- Nissan Altima
Related Codes
See All Codes & Fixes for Your Vehicle
Explore More
Was this helpful?
Send this to whoever is fixing the car — your mechanic, or the person asking what the light means.