The code your getting is for the evaporator emissions system,look for any vacuum hose or hose that's coming from the canister tank,and check to see if its bad or has rotted and fell off,or is closed off,any one of those hoses will cause that to happen,it may just be one that got knocked loose by accident,check any hose that has to do with vacuum or the emission system,a sensor is what caused that code to show up,so it did its job,good luck on finding it,you,ll know the problem when you come to it.
P0456 is small leak in evap may just be a loose or bad gas cap you need a scanner to reset but it will come back on until you fix the problem
On some Dodge Ram trucks, if replacing the gas cap fixes a small leak, then pending P0456 codes will end as soon as the next system emission "self test" indicates a "pass" condition. This will occur if the leak is less than .020. The Check engine light will then go off over time. This self test may take longer to complete in cold weather, or if your gas tank is too full or too empty and/or other driving conditions do not allow your truck's built-in self-test computer to determine if the leak is acceptable. (Even though your tank may still leak, the government has determined that the leak is acceptable if small enough) Note: Just because one can force the check engine light off via a delete button it does NOT necessarily mean it will pass emissions in SOME States. If a M.V. inspector uses a diagnostic code reader and finds a "pending" emission test light "yellow light" instead of green, he MAY request that the vehicle be returned for inspection at a later date after your vehicle has completed its self-test. This depends on the State you live in and their laws.
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Try this if all else fails it might be the problem, http://youtu.be/07ADPtbbwJs
P0456....Evaporative Emission Control System Leak Detected (very small leak)
P0440....Evaporative Emission Control System
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