The right rear motor should rotate clockwise, and the left rear motor should remain stationary:

module.exports.move_left = function(callback){
  
  indicatorLeft();

  enable_1.digitalWrite(1);
  input_1.digitalWrite(0);
  input_2.digitalWrite(1);

  enable_2.digitalWrite(0);
  input_3.digitalWrite(0);
  input_4.digitalWrite(0);

  console.log ("Turn Left")
  callback ("Turn Left") }
}