computer

This is my first post, On a 1990 Grand Prix, can the computer be changed without having to change the prom? My car is slowly losing it's functions: idle control, a/c, now the transmission only has reverse.
Thanks in advance for any help.

There is a prom inside the ECM that will have to be swapped over. just take the 4 screws off the access cover.

The transmission is probally going to be an internal transmission problem not an ECM problem

Thanks for the help, would the transmission go out with no notice? Is it shifted electronicly?

Thanks again