Hyundai Sonata ECT button
 

I have recently purchased a 1997 Hyundai Sonata III and by the shifter it has an "ECT" switch. It is a three position rocker switch with the center (I assume) being off. On one side says "PWR" and the other says "HOLD." It didn't come with an owners manual, so looking it up that way is out of the question.

I assume it has something to do with the shifting of the transmission since when I flip it to "PWR" it seems to have a little more sportier handling. But I am confused as to what the "HOLD" side does. I really notice no difference in its handling. I would appreciate it if anyone could tell me what this switch is for. Also, how does it affect my fuel economy in either position?

Thanks,
Richard