P0442EVAP System Leak Detected (small leak)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- The evaporative emission (EVAP) system stores fuel vapour from the tank in a charcoal canister; a purge valve lets the engine draw it off, and a vent valve opens the canister to fresh air. P0442 reports a small leak; what size that means depends on the maker. Ford detects 0.040 in (1 mm) with the engine running: the vent valve closes, engine vacuum pulls the tank down, the purge valve closes and a pressure rise above 2.5 inH2O in 15 s sets the code (0.020 in is P0456). GM uses the natural pressure change after switch-off for 0.020 in and averages several tests. Pump systems at VW and Audi compare against a reference leak. A worn or loose fuel cap is the most common cause.
- What you may notice
- Check engine light on
- Possibly slight fuel smell
- Readiness or emission inspection not passed
- No change in driving
- Likely causes
- LikelyFuel cap seal worn, wrong or not clicked in
- LikelyCracked or porous EVAP hoses or leaking connections
- PossiblePurge or vent valve does not seal
- PossibleLeak detection pump itself leaking (VW/Audi)
- RareFiller neck corroded, tank or sender seal leaking
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €15 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.