Your 1996 Pontiac Grand Prix SE with automatic transmission won't shift into first gear and all other gears seem fine?

TURN OFF 2ND GEAR START!!! That's the only thing i can think of that could make ONLY 1st gear not work and other work fine. theres a little switch under the steering wheel toward the drivers door, just turn that off so 2nd gear start isn't lit up on the dashboard. have fun.

Answer

you may need to rebuild the grear box or replace the first gear shitfer linkage

Had the problem, replace tranny filter and add some lucas tranny additive. seem to take care of the problem. If you have too, manualy sift to first to start off, this will reduce the heat in the tranny and help to prevent further damage.