From blupupher over at www.chryslerminivan.net
for 2001-2007 years:
Customer Key Programming
You can program new sentry keys to the system if you have two valid sentry keys by performing the following procedure:
1. Cut the additional Sentry Key Transponder blank(s) to match the ignition switch lock cylinder key code.
2. Insert the first valid key into the ignition switch and turn the ignition switch ON for at least 3 seconds but no longer than 15 seconds. Turn the ignition switch OFF and remove the first key.
3. Insert the second valid key and turn the ignition switch ON within 15 seconds. After ten seconds a chime will sound and the Theft Alarm Light will begin to flash. Turn the ignition switch OFF and remove the second key.
4. Insert a blank Sentry Key into the ignition switch and turn the ignition switch ON within 60 seconds. After 10 seconds a single chime will sound. The Theft Alarm Light will stop flashing, turn on for 3 seconds; then turn off.
The new Sentry Key has been programmed. The Keyless Entry Transmitter will also be programmed during this procedure.
Repeat this procedure to program up to a total of 8 keys. If you do not have a programmed sentry key, contact your dealer for details.
NOTE: If a programmed key has been lost, see your dealer to have all remaining keys erased from the systems memory. The remaining keys must then repro-grammed. This will prevent the lost key from starting your vehicle. All vehicle keys must be taken to the dealer at the time of service to be reprogrammed.