To access the solenoids, you'd have to remove the transmission valve body. This is a significant job requiring specialized tools and transmission repair knowledge. It's not something typically done at home unless you have extensive experience working on transmissions.
If you suspect a problem with your transmission shift solenoids, it's best to take your Caravan to a qualified transmission specialist or mechanic. They have the tools, expertise, and diagnostic equipment to accurately identify the faulty component and perform the necessary repairs.