Truck Repair: 1997 F150 Ford, emission control system, charcoal canister

Question
Check engine light came on about 3 days back... I happen to own an OBDII code reader and thought I might be able to figure out the situation and proceed with my own repairs.  The code came up with the generic code of PO455(evaporative emission control system leak-gross leak) Am now in a quandry as what to check for and replace, if necessary, as it says to check owner's manual for repairs. (I learned long ago that an owner's manual is only good for basic fixes, and not much more.)  Any suggestions as to what this code is referencing?  Your advice will be greatly appreciated!  Paul

Answer
Hi Paul,
The vapor canister, or charcoal canister that absorbs the evaporating gas fumes from the gas tank and other places, has a self check feature that will pressurize the system slightly, and measure for leaks.
A hose missing or cracked in that system will allow it to leak during that test, and store a code.
Another thing that will cause that leak and code, is a leaking gas cap.

Van