Hyundai Repair: sonata check engine light, transmission control module, transmission flush

Question
2004 sonata 36000 miles auto trans
check engine light
driving car 70mph on highway, car hesitated for 1 second,check engine light came on. car ran ok
hyundai dealaer replaced solenoid on transmission
last week same thing-hyundai hotline said to flush  trans fluid at my cost since its on 30k maintenace list-severe conditions. i felt it didint apply. had it done anyways. 50 miles laterthe check eng ligtht came on again.will go to dealer tomorrow. any thoughts? car drives fine

Answer
I'll need to know what the trouble code is to have any specific thoughts as to the cause of the problem, but I can say that it sounds like the transmission control module is detecting something abnormal and putting the transmission in failsafe.  

I'd make it clear to the dealer that you think they owe you something at this point since they recommended the transmission flush and it did nothing to address the problem.