273K 92 Honda, running great but won't shift into 3 or 4! Why not?

Your Transmission Control Module is bad. 92-94 models are known for having faulty components in them. I give detailed instructions under the Electrical problem heading, from how to remove the old one, where to buy a rebuilt one and how to basically save you from spending a fortune by doing it yourself.

get diagnostic at Aamco transmission its free.