I have a 2004 Crown Vic lx sport....
My car will not start at all. I have replaced the transceiver, batt, did all the wire checking and the theft light blinks fast, engine light blinks sometime.
I have replaced the ground cable from the batt to the block, check all your grounds....I have a Ford Workshop Manual the next thing is to check the wires leading to the transceiver you might not be getting a strong signal according to this book.
If you want me to scan the pages from the book to check the transceiver wires let me know.