While the older EVAP purge valves never opened at idle, modern EVAP systems are just as likely to purge the canister idling as they are driving down the road. Enhanced EVAP systems were designed to detect vapor leaks as small as 0.020 (twenty thousandths) inch.
Some EVAP systems measured EVAP system flow using a thermistor or some other method. With OBD2 regulations that became mandatory on all cars and trucks by 1997, EVAP systems got an upgrade. “Ported” vacuum is only delivered when the throttle is applied but never at idle.įrom 1970 to the mid 1990s, EVAP systems remained almost unchanged other than some OEMs using electric purge valves rather than vacuum triggered ones. A person who “packs” gas into their tank can cause the canister to become saturated with fuel, causing drivability issues like odd stumbles when the canister begins to purge.Įarly canister purge valves had a ported vacuum line that triggered the purge valve to open a path from the canister to engine vacuum. The canister has an open vent that allows atmosphere to flow through the canister as engine vacuum is applied to the canister’s purge port. A small vapor line runs from the top of the fuel tank to the canister, which retains the hydrocarbon vapors until they are purged by engine vacuum through a special valve. The gas smell from your fuel tank – hydrocarbon vapors from evaporating gasoline – is captured and stored in a special canister filled with fibrous material.
An In-Depth Look at Evaporative SystemsĮvaporative systems have been around since California began requiring EVAP systems on cars in 1970. Although system designs vary, common primary components found within this system include the fuel tank, gas cap, purge valve, vent valve, and EVAP (charcoal) canister. The EVAP system’s primary purpose is to block fuel vapors from escaping into the atmosphere.
The driver should still have the issue checked and fixed immediately to avoid other issues and costlier repairs down the line.
ALLDATA has single-vehicle subscriptions for DIYers that provide detailed factory repair information. Repair manuals, such as those from Chilton, are useful, but an ALLDATA subscription is even better. Other than that, you’ll need to diagnose the code accurately, as outlined above, to be able to perform the most appropriate repair for your specific case.Īlso, keep in mind that all cars are different, so when troubleshooting and repairing diagnostic trouble codes, make sure to consult the factory repair information for your application. You can try tightening or replacing the gas cap, as mentioned, or perhaps even do a visual inspection of the EVAP system components to check for any physical damage that could be causing a leak. Therefore, there isn’t a “magic bullet” fix for the issue. There are multiple underlying causes that could trigger a code P0442.
For an idea of how to troubleshoot the code, check out the videos below: Other than the gas cap, there are numerous potential causes that can trigger the OBD-II code P0442. The code won’t immediately go away on its own. Keep in mind: once you’ve tightened or replaced the gas cap, you’ll have to clear the code with a code reader or scan tool afterward. Check for split or disconnected hoses and/or broken plastic parts. If you have recently hit something in the road or if you’ve had animals chewing on hoses and lines you might be able to spot damage by just doing a visual inspection.
Shops typically use a special machine that pumps the EVAP system full of smoke, which helps tremendously, in finding EVAP system leaks, but P0442 codes can be extremely difficult to find, even for a well-equipped shop. If tightening the cap doesn’t work, you may want to try purchasing and installing a new cap. When dealing with a P0442 code, the first thing a layperson should do is make sure the fuel cap is on tight, because if it’s loose, that could easily trigger the code. Tightening the fuel cap is usually the first thing to do when fixing code P0442. In some cases, you may notice some pronounced fuel odors, although this is less common. Typically, the most common symptoms you are most likely to experience if your vehicle is triggering the OBD-II trouble code P0442 would be an illuminated Check Engine Light or increased vehicle emissions. What are the Common Symptoms of the P0442 Code?