2001 Elantra sticks in 3rd gear auto trans

check engine light comes on and trans. wont shift out of 3rd . Usually if
you pull over an shut car of for a few minutes it will shift again . When
its been doing this I have tried shifting up through the gears mannualy.
But does not shift it in 3rd gear no matter what you do. Can anyone
help???????

 

Your transmission computer is detecting a problem and putting your
transmission in fail-safe. You can turn the car off and restart it and
your transmission will no longer be in fail-safe, but the computer will
return it there once it redetects the problem. Take it in and have it
checked out.

My guess worth what it costs: Input speed sensor.