P0442
Evaporative Emission System Leak Detected (Small Leak)
The Evaporative System (EVAP) prevents the fuel vapors from the fuel tank from escaping into the atmosphere. The EVAP system draws the fuel vapors from the fuel tank and temporarily stores them in the charcoal canister. When the engine is running and other conditions allow, the fuel vapors are purged from the charcoal canister into the engine air intake to be burned. The EVAP system is sealed and the engine computer (ECM) can detect if there is even a small leak. The fault code P0442 means that the ECM has detected a small leak. A gas cap is the first thing to check in this case. Sometimes a gas cap may look OK, but when tested on a special tester it could show a leak. The problem could also be caused by a small crack in a one of the EVAP system tubes or in the charcoal canister, a partially open canister vent valve, loose tube/line connections in the EVAP system, loose seals, problems with the purge valve, problems with the fuel tank, problems with electrical components of the EVAP system, etc. For example, the Mazda TSB (Technical Service Bulletin) 01-052/06 for 2004-2006 Mazda 3 and Mazda 6 recommends checking the purge solenoid valve for intermittent sealing issues.
It’s very difficult to find a small leak in the EVAP system without a special equipment. Sometimes, even with the special testing equipment (usually called “smoke machine”), it could take a lot of time for a mechanic to find a small EVAP system leak. If your car has the code P0442, take your vehicle to a reputable garage or a dealer for proper diagnostic.
A: Check the fuel cap, make sure it’s tight. If you think that it wasn’t closed properly, the check engine light should go off by itself in a few days of driving. If the check engine light won’t go off, there could be a number of other reasons, such as leaking ventilation valve, cracked charcoal canister, cracked or pinched hose, leaking seal, etc.
If the leak is very small, it could be very hard to find. Take your car to a dealer or well-equipped garage that can test your evaporative system with the special equipment.
A: The code P0442 means ‘Small EVAP system leak’. The EVAP system is the one that doesn’t allow the vapors from the tank to escape into the atmosphere; read more above. Checking the fuel cap is the first thing to do. If the rubber seal at the fuel cap looks damaged or there is some corrosion that may prevent the cap from sealing properly, it might be a good idea to put a new cap, which is not expensive. If it was a bad fuel cap that caused the code P0442, the code should clear itself up after a couple days of driving. If the code is still there, there might be some other sources of the EVAP leak. It could be a crack or damage at the charcoal canister, or a small tear at some rubber line, bad vent control valve and few other things. If the cap doesn’t fix the problem, take it to a repair shop, they can check the EVAP system with the ‘smoke machine’ for leaks.