2006 jeep commander 5.7L HEMI 4X4 what is causing this problem..

while driving engine light came on and transmission jumps into 3rd gear, tried shifting into higher gear and it goes right back into 3rd gear, tried lower gear, same thing. checked fuses and wire leading to transaxle, everything seems fine, disconnected battery cables, engine light turned off and transmission was normal again. took it for a test drive and the same thing happened again, engine came on and transmission jumped into 3rd gear. what is causing this problem and is it ok to drive on 3rd gear until
i have it checked out...