In my 91 trooper, im having tranny issues. It still drives and everything but when it decides to pitch a fit, the tranny light flashs at me and I am forced to shift threw the gears Manually. (Starting in low)
I am curious on if this is a regular problem other people have had with this year of trooper. What the problem is and how it is fixed.

 

The transmission is defaulting into "limp mode". You can reset it by turning off the engine and restarting it, but it will likely just do it again. The problem could be caused by low transmission fluid, a computer issue, not being at operating temp, or more likely by something worse. My 91 did the same thing and it turned out to need a transmission rebuild.

 

It's most likely the mode switch located on the driver's side of the transmission behind the manual lever that links to the shifter. To fix it, You must remove the switch which requires removing it's emtire harness from where it plugs in under the hood by the relay box (Black Plug on Bottom), taking the switch apart (be careful not to lose spring and ball bearing [steel ball]), cleaning it with electronics cleaner and/or some 2000 grit wet/dry sandpaper (use dry) to clean the contacts. Inspect the inside of the switch to make sure there are no burnt looking areas. Then re-assemble the switch and replace it on the vehicle. Adjusting it is tricky. You need a 3/16 drill bit to line up a notch on the outside of the switch housing with the part that turns. While doing this make sure your shifter is in neutral. Adjusting this is a bit tricky but once you get it right your problem will be solved. Ypu'll know you have it adjusted right if you can start the car in park and the check transmission light goes off as normal. If it's flashing after re-assembly, it's still out of adjustment.

Do a google search on "Mode switch" for your vehicle and you should find step by step instructions with photos.

Hope it helps