Sounds like you have a good start on your troubleshooting. my guess would be that on such a new van, you are going to find that either the resistor pack is out, or the motor has gone south.
Actually, it could be both if the motor went bad first drawing too much current, then overheated the pack and made it fail.
If you are not under warranty, I would check the pack first as it is cheap. You should find it under the passenger side of the dash mounted into the air box. Look for a 3-5 wire harness attached to the box with 2-3 screws.
Remove the screws and gently remove it. Sometimes you can tell by its appearance or smell if it has failed.
Should this not be the case, I would look at the motor next.
05 Linen Gold Pearl Dodge Grand Caravan SXT 3.8L (hers)
04 Flame Red Hemi 5.7L Dodge Durango SLT