P0442: Evaporative Emission System Leak Detected (small leak)
The computer found a small leak in the EVAP system, about the size of a 0.040 inch hole, during its self test.
What P0442 means
Federal rules require modern cars to detect EVAP leaks as small as about 0.040 inch, and newer cars down to about 0.020 inch. To check, the engine computer closes the vent valve and either pulls vacuum on the system with the purge valve or pressurizes it with a leak detection pump, then watches the tank pressure sensor. If pressure drifts back too quickly, it sets a leak code. P0442 means it found a small leak. RepairPal lists a damaged fuel cap, a distorted filler neck, small tears in hoses or the canister, a bad sending unit gasket, faulty vent or purge valves, a leaking tank, a bad pressure sensor and a faulty leak detection pump. Small leaks are hard to find by eye, so a smoke test is the best tool. Because the test only runs under certain conditions, such as a cool engine and a partly full tank, the code can take days to return after a repair. Drivability is not affected.
Common symptoms
- Check engine light on
- Usually no change in how the car drives
- Faint fuel smell near the car or the fuel door
- Failed emissions or readiness test
- Other EVAP codes may appear at the same time
Most common causes
- Worn or damaged gas cap seal
- Small crack in an EVAP hose
- Small split in the charcoal canister seam
- Leaking fuel pump or sending unit gasket
- Faulty vent or purge valve that does not seal
- Faulty fuel tank pressure sensor
What to check yourself first
Inspect the gas cap seal and replace the cap if the rubber is cracked or flattened. Make sure the cap clicks when tightened. Look at hoses near the canister and filler neck for cracks.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| EVAP smoke test to find the leak | $61-$90 | A smoke test is the standard way to find EVAP leaks. |
| Replace gas cap (shop price) | $138-$150 | A worn cap seal is a common cause of small leak codes. |
| Replace EVAP purge valve | $210-$251 | If the purge valve leaks when closed. |
| Replace EVAP canister (includes vent valve on many cars) | $558-$643 | For a cracked canister or failed vent valve. |
| Replace fuel tank pressure sensor | $356-$457 | If the sensor itself is faulty. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0456 Evaporative Emission System Leak Detected (very small leak)
- P0455 Evaporative Emission System Leak Detected (large leak)
- P0440 Evaporative Emission System
- P0457 Evaporative Emission System Leak Detected (fuel cap loose/off)
- P0451 Evaporative Emission System Pressure Sensor/Switch Range/Performance