Diesel Excursion Won't Start Because of Security System.....

Hello All,
Jim here from Ridgway with a truck that won't start.
This problem showed up 3 month ago and the batteries were low from a bad alternator.
The new alternator and new batteries got'er going until now,
the alternator is good, check by two different shops, the batteries are good, charged by Interstate overnight and hot, yet when the key is turned the theft light flashes quickly.
This happened once and the ignition key loop was replaced, then three months ago it was low volts.
can the security system be by-passed?
I live in the the sticks and am looking to not spend 700 dollars again on a tow truck to tow.

Late answer, but for anyone with the same light. A theft light that flashes fast when you turn the key means the anti-theft system can't read the key, so it won't let the engine run. It isn't a battery or alternator problem, even though low voltage can make it act up.

Try a second programmed key first. If the spare starts it, the chip in the first key is bad. If neither works, the ring around the ignition cylinder that reads the key, or its plug, is next, and a scan tool will show the anti-theft code that tells you which. A mobile locksmith with a Ford-capable tool can program keys where the truck sits, which costs a lot less than a tow.

Dana