I have an Arduino Mega 2560 is the voltage on the this pin 12 I perform the following:
void setup() {
// initialize the digital pin as an output.
// Pin 13 has an LED connected on most Arduino boards:
pinMode(12, OUTPUT);
}
void loop() {
digitalWrite(12, HIGH); // set the LED on
delay(1000); // wait for a second
digitalWrite(12, LOW); // set the LED off
delay(1000); // wait for a second
}
If the LED is across pin 12 & Gnd with no current limit resistor - while pin 13 has a series resistor with the LED - the output pin 12 may have been damaged, and no longer outputting 5V.