2002 elantra occasional shift problems
 

Hello all,
My 2002 elantra with 63000 miles has started this occasional shift
problem. When driving in "d" it will down shift to 3rd and 1st is gone.
I can quickly shut the engine off and all returns to normal.And who
knows for how long. Maybe 10min. maybe 1month. Also the check engine
comes on. And when I shut the car off engine light goes off and every
thing is normal. Check Engine light . Stays off until problem returns.
This has happened about ten times and always 1st and D is gone. Also
this happenes under any conditions (weather wise). Thanks in advance
for any information