99 Mercury Tracer Automatic Tranny probs

Hi there. I bought a 99 Tracer LS from a used car dealer, and he told me that there was a problem with the tranny. He said it had problems shifting in the cold, but told me that after servicing it, he only had problems with it shifting into OD. He told me it needed a new "shift module" which I can only assume means it needs a new TCM. If this is the case, would that cause the car to shift normally but not go into OD? If not, what else do you think could be the problem?