code PO 455 on 1997 Ford Expedition

my OBDII reads this and says large leak/Emissions/ where is the evaporator? I took the gas cap loose and put it back on and cleared the code.started it up,light didnt come on.I have not driven it,wanted to check that canister and hoses.

Asked by for the 1997 Ford Expedition
Most of the time this code is nothing more than what you have already done. If the gas cap comes loose or is not tightend properly, or even if the cap is faulty and not holding pressure this code will come up. This code will not hurt your engine, so now that you have reset the gas cap and cleared the code try driving it and see if the code reapears. If so have your gas cap tested or just replace it they are only about $10 dollars at your local auto parts store.