Theft light flashs ignition wont even click - 2001 Ford Mustang

SOURCE: theft light flashes without key in ignition

Thats normal just tells you system is armed and active

SOURCE: I change the ignition switch and now wont start

Your fob system needs programming. There is a chip in your key that has to be re/programmed to your vehicles anti-theft system. You may call a special locksmith or tow to dealer to perform this. Hopefully this helps

SOURCE: Theft-deterrent system problem

let it sit for about an hour, untouched to let it clear out of theft mode. If it doesn't start with a programmed key after that, you may have to take it into a shop and have it looked at. It may just be a bad transceiver but if any piece of the system has been replaced the keys have to be programmed with a dealership scan tool.

SOURCE: when ignition is turned theft

It thinks you are trying to steal it, Are you using the same key you always use? I would find a good garage that can check it for you.

SOURCE: The car wont start, the

TRY REPROGRAM KEY .PUT KEY IN IGNITION SWITCH TURN IGNITION SWITCH ON POSITION 20 SECONDS DONT START ENGINE WAIT 20 SECONDS TURN OFF SWITCH THEN TURN SWITCH BACK ON 20 SECONDS WATCH THE THEFT SECURITY LIGHT BLINKING.WHEN THEFT STOP BLINKING VECHICLE WILL CRANK.IF LIGHT STILL BLINKING.TRY FEW MORE TIMES KEY IN SWITCH ON POSITION FOR 20 SECONDS.MAKE SURE YOU HAVE THE CORRECT CAR KEYS IN SWITCH IF NOT WRONG SET OF CAR KEYS WILL SET OFF THEFT SECURITY SYSTEM.IF KEY RESETTING TRICK DONT WORK.CHECK BATTERY POWER MAKE SURE YOUR BATTERY HAS 12.5 VOLTS AND CHECK SECURITY THEFT FUSE.IF ALL LOOKS GOOD YOUR SECURITY HAS TO BE CHECKED OUT AT THE DEALERSHIP.