That is a possibility. If the transmission computer detects a problem it goes into "Limp home mode" and not go past second gear. Here is a site with diagrams of the trans. http://cloud.prohosting.com/davenger/a604digrams.html ...Good Luck...
My 97 Dodge Caravan has been working fine. However last night when I was going out my speedometer was not working and my engine sounded as if it was stuck in gear. I was able to drive fine (up to about 40mph) where I needed to go BUT it sounded a bit revved. Is it my speed sensor and where is it located