I have a 2000 Expi that has the Ford System 4 Security System installed by the Dealer when new.
I've had this vehicle since 2003 as 2nd owner and recently it needed a jump start. After that the Sys 4 Alarm went crazy and I was only able to start the car after pushing the Emergency Override Button.
https://www.ford-trucks.com/forums/9...m-removal.html

I have the Owner's Guide for this system but that does not explain how to re-set the system back to default.
I found the answer here:
http://www.f150online.com/forums/lig...ystem-4-a.html
I followed his step-by-step procedure and it worked! Problem solved for me.

I have copied Sycoholic's 're-initialize' procedure here in case someone else has this trouble. Just passing along this info as a little payback for the help the Forum has been to me.

Re-initialize Ford System 3 (or 4) Alarm System:
<hr style="color: rgb(255, 255, 255); background-color: rgb(255, 255, 255);" size="1">Disconnect the battery. Wait 2 minutes for the module to lose all traces of voltage.
Turn the ignition key to the RUN position.
Reconnect the battery.
Shut the key OFF and press LOCK on the drivers door switch.
It's called reinitializing the alarm.