Arduino Mega enable pin connected to timers

I was using pin 8 for something else, I have a stepper motor connected to the arduino, pin 8 tells the direction, either 0/1, and pin 4 supposed to be an enable square sign, every time it goes HIGH the motor should make a step.

Even if I define pinMode(4,OUTput); i can't see the square sign on it

I know timer0 and timer1 might be used for other funcitons, i am just getting started, I will use timer2-6 later on.
So quaestion is the same, if pin 4 is conencted to tiemr0, why can't I see square sign on the pin?