It is possible for just one line on the PCM to be bad.....however, it is best to see if there is something else causing the failure.....so you don't spend the money on a expensive replacement that is not needed.....and does not solve the problem.
A wiring diagram will let one know what pin on the OBDII connector goes where.....and it can then be followed, using the wire color and pin-out locations for various connectors.
Now....cruise control.... A VERY common cause of this is a leaking brake pressure switch.
This switch is located on the bottom of the brake master cylinder.....brake fluid leaks into/through the switch....causing problems just a you describe.
The solution is to replace with a new switch, which comes with a adaptor wiring harness that matches the connector on the new switch up with the connector on the wiring harness.
This is a simple repair that you can do yourself......after buying the "kit" from the dealer.
I have pictures posted in the pictures that the link in my signature takes you to.....that show the brake pressure switch replacement process.......which, though on my '96, will be applicable to your 2000 model year (though many other things in my pictures will be different).
Extended waranties are usually not worth it.
There are a LOT of companies that are trying to sell you extended waranties for your vehicle.....I STILL keep getting notices in the mail telling me that my factory waranty is about to expire......to act NOW to continue my coverage.
My vehicle is a 1996 with over 208,000 miles on it.......so the factory waranty is long gone.....forgotten.....history.....so it is certainly not FORD Motor Company that is sending me this stuff.......and you want to be certain of WHO is providing the coverage....and what hoops you have to jump through to get a repair covered.
They certainly will be nice about taking your money.....but will they be nice when you expect them to pay out?
One has to carefully read ALL the fine print......and see what is covered.....and what is not.....and what the process is to get the repair covered.
I think that the most important thing to have is a local shop that you can TRUST to be honest and competent in servicing your vehicle.
That....along with keeping super on top of routine maintenance will help you get the most out of your vehicle.