94 gt tranny issue

switched 3100 motor, tranny snd subframe from one 94 gt to another. ran fine for two days. then engine light came on and shifted from 1st to second at 2000 rpms and wouldnt never downshift. i was boggled. then i switch the module that sits over the shifter linkage. problem fixed as of now. does that sound like a right fix or just a lucky switch. engine light is still on though.

the check engine light probley will stay on till you clear the trouble codes. if you dont hav a TOOL then disconnect the battery for 10-15mins.

The module switch still working? If so I'd say thats a fix. It controls the trans. shifting I think. It may hav just taken the cars CPU a while to figure out whats what and why is this differant motor in here.