Modern vehicles are designed with an evaporative emissions system, also known as an EVAP system. When you pump fuel into your gas tank, there are vapors which emit from the fuel. If these fuel vapors were to escape your gas tank and reach the outside air, it would have a negative affect on the environment. The purpose of the EVAP system is to block these vapors so that they don’t leave your vehicle. The EVAP system basically captures these fuel vapors and then temporarily stores them. As you continue to drive your vehicle, the vapors will enter the internal combustion chamber of your engine where it will get burned along with the regular fuel and air.
The three main components of the EVAP system are the charcoal canister, purge solenoid, and canister vent valve. The charcoal canister is what absorbs the fuel vapors and keeps them stored. Once fresh air hits the canister, the vapors flow into the engine. The purge solenoid is what causes the purge valve to open. That way, the fuel vapors will have an entryway into the engine. The canister vent valve is part of the self-testing mechanism of the system. It keeps air away from the charcoal canister so that the system can accurately test to see if there are any leaks.
Trouble Code P0456
When you turn off your engine, the powertrain control module analyzes the EVAP system as it helps shut it down. The module checks the system for any leaks or other problems. If the module finds there is a leak in the system, it will generate the following diagnostic trouble code: P0456. This is a code that you may or may not be able to see on the dashboard. Some model vehicles will display these trouble codes right on your dashboard screen. In other vehicles, you will need to attach a diagnostic scanner to the powertrain control module to discover this code.
How will you know when the right time is to use the scanner? Well, just watch out for certain symptoms which would indicate a leak in your EVAP system. Some of these symptoms include the Check Engine warning light turning on and the inability to pass your emissions test. If you go to inspect your vehicle, you may find the EVAP hose is leaking or that the gas cap of your fuel tank is loose. Sometimes the vent valve or purge valve might be damaged as well.