I bought a used 1994 Caravan that had the limp mode problem, with no check engine light and no error codes either using the key method or when read by a transmission shop with the proper equipment.
IT would go into limp mode occasionally, and sometimes repeatedly.
I bought a used transmission control module ($9.50), and it was better, but still had a problem. The replacement was from a '95, but the same update version. I then bought another TCM from a van manufactured the same month as mine, with no indicated updates. Using that TCM, I have had no problems for a week, so I'm hopeful that the problem is now gone.
FWIW.