Code P1451 on 2002 Taurus SES

Check engine light on and code is P1451. I have been told its one or all four things: 1. Gas cap, 2. Evap Canister vent solenoid, 3. Evap purge solenoid, 4. Evap canister. I am trying to fix this problem on the Taurus. I have changed the Gas cap and this did not solve the problem. The other three things on the list: Are these three separate things? Or are they part of the same thing? Please advise so I know which parts to purchase.

Have you inspected the EVAP canister and piping to make sure it's not damaged?

At least on other makes and models, it's not uncommon for the solenoids to fail, typically the one that's under the car and exposed to road salt, etc.

-Rod