I have an 07 Journey. There is a shut off valve under the sink. They are small in a small plastic pipe. Look up under/behind the sink and you should find it. Actually there are two. One goes to the water filter and the other to the ice maker.
All the above are great answers but also, do check the automatic shut-off arm in the ice tray/box to make sure it's down and not in the up position. If it's in the up position, it's telling the ice maker to shut down 'cause it thinks the ice tray is full.
2004 ITASCA HORIZON 36GD, 2011 GMC Sierra 1500 4x4 Toad '08 GL 1800 Gold Wing
Retired-29.5 yrs, SDFD, Ham - KI6OND
Me, Karla and the Sophie character, (mini Schnauzer)