[quote=jimmer;81781it takes at least 2 keys allready programed keys for you to do it yourself, [/quote]

Just to be clear:
1997-1998 Expy, which has the PATS Type "A" System only requires ONE key and no scan tool to add another programmed key. It can be programmed for up to 16 keys.

1999 -2002 uses the Type "C" PATS and requires TWO working keys and no scan tool to add another programmed key. It can be programmed for up to 8 keys.

2003 - 2005 uses the Type "E" PATS and requires TWO working keys and no scan tool to add another programmed key. It can be programmed for up to 8 keys.

If the maximum number of keys have been programmed and you need to add another key, a scan tool is needed to erase key memory.

The Type "A" System is a stand alone system and the type "C" system is integrated into the instrument cluster. They will not keep the vehicle from cranking over with an invalid key, but will disable the fuel injectors.
The type "C" system is integrated into the PCM and has starter interupt capability if an invalid key is used.