Hyundai Repair: shifting, sonota, engine computer

Question
The check engine light only comes on when it shifts hard otherwise when it shifts nornal it off.
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-----Question-----
My hyundai, when its cold sometimes will hesitate to shift to second and when it does it's a really hard bump type shift or rough, and it's sluggish when I press the accelerator also sometimes if I take my foot off the accelerator it will slow down way to fast almost to a stop. This is a 2000 sonota model, 129k automatic, could maybe the trans screen need changing, the fluid looks good and not burnt smelling.
-----Answer-----
It sounds more like an issue with one of the transmission sensors.  Is your check engine lamp on?  If so, you should have your engine and transmission diagnostic trouble codes read.

Answer
You should have the trouble codes checked.  The transmission computer is seeing something abnormal, causing the transmission symptoms, and it's asking the engine computer to turn on the check engine lamp to notify you it sees a problem.  It's also putting the transmission in failsafe (third gear only) when the problem occurs to enable you to continue driving the car.  The trouble codes will be the key to determining what the transmission computer saw that was abnormal.