What does the at button on the dash of a 2001 Mitsubishi Montero do?

My 2000 has it too. Haven't tried it to see if a 'hold' light lights up, but the owner's manual also says something about this light. It's called an A/T mode change switch. In the book, they only repeated the info about the light. http://www.Mitsubishi-forums.com/t3671-rvr-a-t-switch.htm I have a 2001 Mits Montero Sport, and I have found that when you are climbing a grade, your 'automatic transmission' will automatically downshift when pressing the accelerator to the floor. If you don't want it to shift on it's own, use the A/T button to hold your transmission in the gear you want it. A hold light will illuminate on your dashboard underneath the speedometer if the A/T light has been depressed. Hope this helps!