Double traction indicator light is flashing

Hello friends, I tell you a montero 1993 and a detail arose, when I take out the 4x4 and return to the rear -wheel drive only, they are blinking the front wheel lights as if it had not come completely from the integral. I mechanically notice that they only traction the rear when it is in position, but it bothers the flash of the lights on the board.
Did anyone have this problem? Will it be a sensor ??
I am waiting for comments.
Thanks

Paul