What does this button do?

[exploremore77]

2005 Explorer XLT. To the left of the steering column there’s a dashboard button that has a backlit "Off" indicator on the top half of the button. The bottom half of the button has a P with vertical lines radiating out of it to the right down to a triangle with a line under it. The "Off" indicator is dimmed by default, but it lights when the bottom half of the button is pressed. What does this button do?

 

[Asmegin]

Rear parking sensors. If it lights up by default when you shift into reverse, your sensors aren't working.

 

[Limited02]

Rear parking sensors. If it lights up by default when you shift into reverse, your sensors aren't working.

Bingo!!!

It's to be used when you are backing a trailer up and don't want to hear the reverse sensors beeping. And yes, if you go into reverse and the OFF lights up automatically, your sensors are not working.