This info is found on net wrt 2nd and PWR button
2nd button is for snow/ice starts. Keeps the wheels from spinning so much.
The power button holds the vehicle in each gear a little longer before shifting. Good for towing.
I use the 2nd button in heavy, slow traffic on the freeway. It prevents constant shifting between first and second.
It's not unusual to have a loose connection on the underside of the buttons. Remove the screws holding down the shroud over the shifters and check the electrical connects going to the buttons. It's a start.
FYI, I keep the power button on except in low range where I find it causes harsher shifting.