The PATS system works by sending out a RF signal that is picked up by the transponder in the key. The transponder then returns a unique RF signal to the vehicle's computer, giving it the ok for the vehicle to start and continue to run. This frequency of your transponder key is recorded in the PATS module during a "training" mode. If the transponder keys you have are not recorded in the PATS module you will have to have the old keys erased and the new keys programmed. If the PATS module recognizes a "foreign" frequency from the transponder key, or no signal at all, it will interrupt the fuel injector circuit and indicate a "failure to recognize" via the THEFT light on the dash.
Most Locksmiths will "teach" your PATS system your keys for a price cheaper than the dealer. Also, Locksmiths can come to you, meaning you don't have to worry about towing the truck to the dealer. My PATS programming cost me $40 for the first key, and $10 for each additional key. The Service Call fee was $45, so for less than $100 I got my truck running. It would have cost me that much to have it towed to the dealer, who wanted almost $250 to program 2 keys.
The Black Beast 5.0
Better to Have Horsepower and not Need it, than to Need it and not Have it!
2000 Ranger Sport - 5.0L V8 - 8.8 LS rear