Red anti theft on dashboard of 2000 crown victoria blinking real fast

Question edited for clarity.
Question moved to model category.

Did you disconnect the battery recently before this happened? Is the anti theft light flashing?

https://www.google.com/search?q=1999+Ford+Crown+Victoria.+Cranks%2C+no+start

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It will never start until the codes are canceled in its computer brain. Takes expensive specialty tools. A dealer can do it but you have to get it to them. A less expensive way is to call and ask a mobile mechanic if can do it. Not all of them can. Replacement keys fob are not expensive online but they also need reprogramming also.

The service and repair manual with diagram will help you to locate and fix the problem easily on your own and you will get the manual from the given link https://toolsnyou.com

Is the theft light on steady when trying too start the vehicle or does it flash ? Or not on at all ?

Do you have another key for the car? Try that. If not you'll have to have the keys programmed to the car at the dealer.

security light

Usually means the sensor in the lock cylinder is not reading the code in the key.
If the pass key system does not get the right signal from the key the truck will not start.
You might try taking the key off your ring - put it in the lock and turn the switch on - but don't crank it for at least a minute.
There are procedures to reset the anti-theft online - - if you do a search for resetting anti-theft F150 you can read them.

sounds as thought the computer is not working, you can disconnect the battery for a 10 minutes or so and then reconnect it and see if it will start. does this have a FOB if it does then the anti-theft is the problem, in other-words if you locked it with the FOB and then used the keys to unlock it can cause this problem. Hope this helped Tim

The 5 digit entry code is in the trunk, on the left hinge arm that holds the trunk lid.