One of the LEDs on my Arduino is very dim I made a vibration sensor using an Arduino. It is connected to an Android app. When the start button is pressed on the app, a red light LED turns on (stand by), and after 2 - 5 seconds, the red LED turns off and a green LED turns on (meaning the system is ready). The green LED turns off if the sensor detects a vibration. The green LED works perfectly. However, the red LED is always dim. I've tried testing the red LED separately, it works fine. I've tried changing the pin it's connected to, it's still dim. I've included my code below if it helps.

Thanks in advance.

int ledPin = 13;
int ledPin2 = 9;
int EP = 7;
int cal = 500;

void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(EP, INPUT); //set EP input for measurement
  Serial.begin(9600); //init serial 9600
}

void loop() {
  if (Serial.available()) {
    char c = Serial.read();
    if (c == '1') {
      cal = 100;
    }
    if (c == '2') {
      cal = 200;
    }
    if (c == '3') {
      cal = 300;
    }
    if (c == '4') {
      cal = 400;
    }
    if (c == '5') {
      cal = 500;
    }
    if (c == '6') {
      cal = 600;
    }
    if (c == '7') {
      cal = 700;
    }
    if (c == '8') {
      cal = 800;
    }
    if (c == '9') {
      cal = 900;
    }
    if (c == '0') {
      int randm = random(2, 6);
      int x = randm * 1000;
      digitalWrite(ledPin2, HIGH);
      delay(x);
      unsigned int tm = millis();
      digitalWrite(ledPin, HIGH);
      digitalWrite(ledPin2, LOW);
      while (1) {
        long measurement = TP_init();
        char br = Serial.read();
        if (br == 'x') {
          break;
        }
        if (measurement &gt; cal) {
          digitalWrite(ledPin, LOW);
          unsigned int out = millis() - tm;
          unsigned char i = out;
          Serial.print(out);
          break;
        }
      }
    }
  }
}

long TP_init() {
  delay(0);
  long measurement = pulseIn (EP, HIGH);
  //wait for the pin to get HIGH and returns measurement
  return measurement;
}
You need to add this line for the other LED pin:

pinMode(ledPin2, OUTPUT);