Stopped shifting with no warning signs

You could have a faulty TCM (Transmission Control Module). The TCM is located on the passenger side fender, inspect the wire harness and the fuses under the hood by the battery. At worst the wore harness at the transmission may have gone bad and needs to be inspected for any damages like corrosion or break. Start with the simple and check all your fuses and then move on to inspecting the wire harness at the TCM, disconnect the wire harness at the TCM and inspect for any damages and reconnect. Once that has been determined that thing are good, move on to the wire harness connection on the transmission, I believe it's going to be on the driver's side right under where the battery is. Look for any damages once again and repair any damages, after all has been done. The only thing next to do is bite the bullet and take it to a transmission shop and have them scan the ECM for the Transmission performance ti find the problem. Oh and almost for got, was the transmission fluid check for proper level. Good luck and keep me posted and thank you for using Fixya.

There is several issues that can be the problem firts off! check the tranny fluid level at the transmission dipstick if it is low? then add fluid and those trannys take a special blend of fluid to operate successfully that can be bought at any auto parts store ..Do Not! put dextron 3 in it ! also remove the dipstick and smell the fluid on it if it smells burnt then you have internal damage that should be repaired byt a transmission tech also if the fluid level is full? and clean? then check/ change the filter and fluid! all automatic transmissions irreguardless of what has been told!! should! be changed once every two years reguardless of milage transmission fluid like egine oil breaks down with time!! and use! and changed the viscosity rateing !

Check the transmishion flud if its a qt or more down that would keep it from shifting right