Transmission won't down shift

What is your question?

I was going down the road at about 55 mph and my Jeep all of a sudden reeved up and wouldn't down shift. I stopped and turned Jeep off and it drive good until I reached higher speeds and it wouldn't down shift again. Check engine light is on steady and it's an automatic.

What makes this problem better or worse?

Worst when I reach the 4th gear. Goes away when I turn Jeep off and back on.

How long has your 2008 Jeep Wrangler had this problem?

Few weeks