I have a 2000 Excursion and a 2009 F-250. If I have identically-keyd ignition cylinders, can I program the same key to both trucks?

 

I would think that when you program the second truck it will erase the first one.

 

I was under the impression it was the truck that was programmed to accept the key's RFID, not the other way around

 

You may be right. I was thinking of the fob.

 

With some "cheating", you can absolutely use the same keys on both trucks (after the cylinders are matched).

The 2000 used an H72 40-bit key blank, the 2009 would have used an 80-bit H84/H92 which is supposed to be compatible with 40-bit keys used earlier. The hard part is that I haven't come a source that is definitive on which ones. The other complication is that, according to at least one source I came across, the H92, if programmed into a 40 bit system, will lock the H92 into 40-bit mode making it not usable on 80-bit systems. The chip in the H92, the 4D63, includes a writable EEPROM that the vehicle programs during the on-vehicle key programming. This renders the key usable only on that vehicle unless re-programmed to a different vehicle which causes the key to be married to THAT vehicle, basically forgetting the previous vehicle. This prevents, in normal Ford customer vehicles, programming one key to multiple vehicles (when equipped with 80-bit systems).

Simplest way of "cheating" is to do a "redneck PATS bypass" on the 2000. Dismount the PATS transceiver from its position around the ignition cylinder, affix a pre-programmed key (or its transponder chip) into it so it is read accurately and won't dislodge, then mount the whole thing as high up out of sight as possible. The H84/H92 key from the 2009 would then actuate the 2000's ignition switch while PATS reads the old transponder and everything is happy. Of course, as anything "redneck"ed, there can be a future downside, If a component of the PATS system has to be replaced and PATS must be re-programmed, the bypass will need to be reverted or accommodated.

The 2000's key will never satisfy the 2009's PATS system so it can't go that direction. Use the 2009's keys as your "master" for the cylinder re-keying in the 2000.