Only Have 1st Gear In Ally

[chevy22]

Ok...hear's the story. I pulled my 35 ft fifth wheel about 100 miles this past thursday through slightly hilly terrain on our way to campgrounds. Spent the weekend camping and even had the truck unhooked and used it to make a beer run with no problems. Hook up this morning and as we leave truck will not shift out of first gear. I have reverse and first and that is it. Service engine light is on, no fluids leaking and levels are correct, unhooked battery to try to reset code (????), and unhooked plugs from module on side of ally with no success. Thank God for friends. My buddy brought another truck on his trailer and we got them both home but I have a 8.1 with ally stuck in first and maybe even worse had to drive a dodge home. I heard occasionally the "module" on side of tranny goes bad. Anyone heard of this. Thanks.