P0442

P0442 is the small-leak code — the EVAP system is leaking somewhere in the range of 0.020 to 0.040 inches equivalent diameter, which is a leak you cannot hear or feel but the ECU can detect by watching how fast the system loses vacuum during the leak-check phase of a drive cycle. This is the most common EVAP code in the wild because the threshold is tight enough that a tired fuel cap O-ring will trip it, but loose enough that the leak source is usually still findable. Cheapest first check is the fuel cap: $5-30, two-minute swap, clears the code on roughly 35-45% of P0442 vehicles. If the cap is good, smoke test the system from the service port — the smoke will pool and escape from the actual leak, which on most vehicles is the charcoal canister body, a cracked vent or purge line, a degraded O-ring at the fuel filler neck, or a purge solenoid leaking through. Smoke is the 80%-of-causes test; nothing else finds a 0.020-inch leak as reliably or as fast.

Vehicle-specific tendencies: 2005-2015 Toyota Camry, Corolla, RAV4, and Lexus ES/RX throw P0442 most commonly from the fuel cap (Toyota's cap O-ring hardens around 80-120k miles) followed by the canister vent solenoid. 2003-2010 Ford 4.6L vehicles crack their charcoal canisters — the plastic gets brittle from underbody heat and a hairline fracture in the canister body is a textbook P0442; replacement canisters run $150-300. 2007-2014 GM Silverado/Sierra/Tahoe trucks throw P0442 when the vent solenoid gets dust-packed; the truck won't fully seal during the leak test even though there's no actual leak — clean or replace the solenoid and the code clears. 2008-2015 VW/Audi LDP failure shows up as P0442 because the pump cannot maintain test pressure. 2012+ Hyundai/Kia with FTPS issues report false low pressure and trip P0442 even on a sealed system; the FTPS is the fix. Repair range: $5 cap, $40 vent solenoid clean, $150-300 canister, $80-150 FTPS, $300-500 LDP.