P0442 = Evaporative system small leak detected
The vehicle's PCM (powertrain control module) tests the evaporative emissions (EVAP) system for large and small leaks among other conditions. In the case of this DTC, it indicates a fuel vapor leak in the EVAP control system. It means a very small leak has been detected. In fact, the leak can be from a hole as small as 0.04" in diameter.
The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine to be burned. That results in decreased vehicle emissions.
A code P0442 most likely means one or more of the following has happened:
A loose or improperly affixed gas cap
A non-conforming gas cap (i.e. not factory/original brand)
A small leak/hole in a fuel vapor hose/tube
Other small leak in EVAP system
Faulty vent o-ring seal
Defective vent valve
Defective purge valve
Defective leak detection pump
With a P0442, the most common DIY repair is to: Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back.
Otherwise, replace the gas cap (recommend an OEM original part, not aftermarket part), or visually inspect the EVAP system for cuts/holes in tubes/hoses.
More advanced troubleshooting steps include:
Using an advanced scan tool, perform an EVAP leak test
Verify operation of the EVAP purge solenoid / valve
Perform a smoke test to see where the leak is