LinkNode D1 Serial stops working when using pinMode

The following code works. I get an output in the console every second of "Hello" and then the analogValue of the photoresistor.

int greenLedPin = D1;
int yellowLedPin = D2;
int redLedPin = D3;

int lightSensorPin = A0;
int analogValue = 0;

void setup() {
  Serial.begin(9600);
//  pinMode(greenLedPin, OUTPUT);
//  pinMode(yellowLedPin, OUTPUT);
//  pinMode(redLedPin, OUTPUT);
}

void loop() {
  analogValue = analogRead(lightSensorPin);
  Serial.println("Hello.");
  Serial.println(analogValue);
  delay(1000);
//  digitalWrite(greenLedPin, HIGH);
//  digitalWrite(yellowLedPin, HIGH);
//  digitalWrite(redLedPin, HIGH);
}

Now as soon as I uncomment the pinMode commands nothing shows up on the console.

int greenLedPin = D1;
int yellowLedPin = D2;
int redLedPin = D3;

int lightSensorPin = A0;
int analogValue = 0;

void setup() {
  Serial.begin(9600);
  pinMode(greenLedPin, OUTPUT);
  pinMode(yellowLedPin, OUTPUT);
  pinMode(redLedPin, OUTPUT);
}

void loop() {
  analogValue = analogRead(lightSensorPin);
  Serial.println("Hello.");
  Serial.println(analogValue);
  delay(1000);
//  digitalWrite(greenLedPin, HIGH);
//  digitalWrite(yellowLedPin, HIGH);
//  digitalWrite(redLedPin, HIGH);
}

Any idea what might be going on?