I have a 97 expedition that I replaced the ignition cylinder and key because my keys were stolen. Now the car will crank but not start and the theft light flashes. Any ideas on how to fix this?

Dealer has to program keys to vehicle

YouTube has info on programming but the dealer really needs to do that for security reasons. Taylor Ford is pretty fair for a dealership

Sorry, no ideas on this. The comment above by K.R. sounds reasonable.

You have to have the correct transponder key cut or resistor key to match it should be in your owner manuals some have resistors keys may be able to program that one but I think you do need a original. You tube or Google may help.

Dealer has to remove old key chips from computer in your expedition and reprogram it.

You would want to direct your question to the service department

It has anti theft security sensor which may need to be reset, probably.