I thought that a bad jumper (SDA or SCL) might cause that to happen, but testing on my setup still prints OKAY, Also, IN LOOP in serial monitor even with one or both disconnected. So, I have no idea what is going on.
Try this. Run this I2C address scanner to see what comes up. Run the scanner, cut and past the serial monitor output to a new post, please.
// I2C scanner by Nick Gammon. Thanks Nick.
#include <Wire.h>
void setup() {
Serial.begin (115200); //***** make sure serial monitor baud matches *****
// Leonardo: wait for serial port to connect
while (!Serial)
{
}
Serial.println ();
Serial.println ("I2C scanner. Scanning ...");
byte count = 0;
Wire.begin();
for (byte i = 1; i < 120; i++)
{
Wire.beginTransmission (i);
if (Wire.endTransmission () == 0)
{
Serial.print ("Found address: ");
Serial.print (i, DEC);
Serial.print (" (0x");
Serial.print (i, HEX);
Serial.println (")");
count++;
delay (1); // maybe unneeded?
} // end of good response
} // end of for loop
Serial.println ("Done.");
Serial.print ("Found ");
Serial.print (count, DEC);
Serial.println (" device(s).");
} // end of setup
void loop() {}