1994 oldsmobile with electronic trans?

we have a 1994 oldsmobile cutl cierra, it started out kicking in and out of overdrive on the highway. then gradually, when the engine was cold it wouldn't shift out of first. and now it won't shift at all. we changed the fluid, it don't smell or look burnt. are there electonic modules in the that will keep it from shifting. this is a remaned from gm. thank you