GT-511C3 not opening

Greetings. This is my first post on any forum, necessitated by my first foray in to the fingerprint sensor. I have to incorporate the fingerprint sensor GT-511C3 with the Arduino uno for my sister's project. But i am facing the problem when i connect the sensor to arduino uno board. Gives me the error avrdude: ser_open(): can't open device "\.\COM3": The system cannot find the file specified.

Though when i disconnect the sensor the board works perfectly fine. But the problem starts when i connect it to the board. Also cannot open the sensor throught the demo software of the GT-511c3(though a green LED shines on it)

I made a number of prerequisite searches for "can't open device," without finding a solution to my problem.

The Error: Arduino: 1.6.7 (Windows 7), Board: "Arduino/Genuino Uno"

Sketch uses 2,218 bytes (6%) of program storage space. Maximum is 32,256 bytes. Global variables use 256 bytes (12%) of dynamic memory, leaving 1,792 bytes for local variables. Maximum is 2,048 bytes. avrdude: ser_open(): can't open device "\.\COM3": The system cannot find the file specified.

Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

This report would have more information with "Show verbose output during compilation" enabled in File > Preferences.

Thanks

disconnect scanner from pins 0,1 while uploading code. It may accept software serial ?