The evaporative emissions (EVAP) system is designed to prevent fuel vapors from escaping into the atmosphere. To accomplish this, the vapors are captured and stored. Then, when the time is right, the vapors are pulled into the engine and burned.
Code P0456 is typically caused by one of the following:
Begin by checking the gas cap to make sure it’s tight. Even if the cap seems secure, it may not be sealing well. Gas caps are inexpensive, so if you have any doubt, replace the cap and clear the code.
Next, perform a visual inspection of the EVAP system, looking for broken hoses or visibly damaged components. If a problem is found, repair it and clear the code. If nothing is found, check for technical service bulletins (TSBs) regarding the issue. If these preliminary measures don’t yield any results, you’ll need to move forward with a step by step system diagnosis.
The following is a general diagnostic procedure. Refer to the manufacturer’s repair information for vehicle-specific diagnostic information.
It’s a good idea to consult the factory repair information and wiring diagrams before proceeding.