1996 Grand Am will go in reverse but not drive. Is there a sensor that would cause this?

It is probably a problem in the transmission valve body or shift linkage. a check ball may be stuck preventing fluid flow. Does it go into 1st and 2nd?

As Rob said. Check the shift linkage. You'd be amazed at how small of an object would jam up the shift linkage. Check the tranny side first. If you have a helper get them to move the shifter while you watch. If there is nothing visible check the console. Worst case it is internal in the tranny.

It did go into first and eventually drive about a year ago (It has been sitting since then). I am now trying to get it back on the road. Please explain the shift linkage a little more. I have never worked on that part of a car. Thanks a lot.

The shift linkage is on top of the transmission. it's easy to spot. have someone shift the gears and you will see it move. If you disconnect the cable you can move it by hand and should be able to feel it "click as it engages each gear. if done while running make sure ebrake and foot brake are held so you don't get run over. If you can get it to shift this way then replace or adjust the cable.

Thank you.

Its a pressure contol solenoid that causes your pontiac transmission problems of not going in any foward gear . And just going in reverse. Now your pontiac or GM transmission at a qualified auto repair shop to replasce the pressure solenoid costs between $300 and $500 dollars and this will correct that problem. Good luck i hope this helped you