What Does P0442 Mean?
The PCM has detected a small leak in the evaporative emission control system. During the EVAP system self-test (typically run during specific driving conditions), the system was unable to maintain the required vacuum or pressure, indicating a leak equivalent to approximately 0.020–0.040 inches in diameter. This is often caused by a fuel cap issue or a small crack in an EVAP hose. The driver may notice a faint fuel smell.
Common Causes
30%
Loose, worn, or cracked fuel cap gasket
25%
Small crack or deterioration in an EVAP system hose
15%
Faulty EVAP canister vent valve allowing a small leak
15%
Leaking purge valve (not sealing completely when closed)
15%
Cracked or leaking fuel tank filler neck or O-ring
Diagnostic Steps
1
Start with the fuel cap — remove, inspect the gasket for cracks or deformation, reinstall firmly until it clicks, clear the code, and complete a full EVAP monitor drive cycle.
2
Perform a smoke test by sealing the EVAP system and introducing low-pressure smoke through the test port — carefully inspect every hose connection, the canister, vent valve, purge valve, and fuel tank filler neck for smoke escaping.
3
Check the EVAP canister vent valve by commanding it closed and monitoring system vacuum — any vacuum loss indicates a leak at or past the vent valve.
4
Inspect all EVAP hose quick-connect fittings for proper seating — push each one in firmly and verify the retaining clips are engaged.
5
If the smoke test does not reveal the leak, apply a small amount of pressure (no more than 1 PSI) to the EVAP system and use an ultrasonic leak detector around the fuel tank area, filler neck, and canister.
Estimated Repair Cost
$20 - $400
Parts + labor, varies by vehicle and location
The PCM has detected a small leak in the evaporative emission control system. During the EVAP system self-test (typically run during specific driving conditions), the system was unable to maintain the required vacuum or pressure, indicating a leak equivalent to approximately 0.020–0.040 inches in di...
The most common cause of P0442 (Evaporative Emission Control System Leak Detected (small leak)) is: Loose, worn, or cracked fuel cap gasket
Typical repair costs for P0442 range from $20 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive. A small EVAP leak allows minor fuel vapor release into the atmosphere. No engine performance or safety impact. The most common fix is simply replacing the fuel cap.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0442 to identify the root cause.
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Quick Info
Category
Powertrain
System
Evaporative Emission (EVAP) System
Difficulty
Type
Generic (SAE)
Recommended Tools
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