avrdude: ser_open(): can't open device "\\.\COM3": Access is denied.

Hi! I'm updating my 3D printer and I tried uploading and got this error saying access is denied. Here is the error message below. Thank you :slight_smile:

Arduino: 1.6.9 (Windows 10), Board: "Arduino/Genuino Mega or Mega 2560, ATmega2560 (Mega 2560)"

Sketch uses 117,850 bytes (46%) of program storage space. Maximum is 253,952 bytes.
Global variables use 4,215 bytes (51%) of dynamic memory, leaving 3,977 bytes for local variables. Maximum is 8,192 bytes.
C:\Program Files (x86)\Arduino\hardware\tools\avr/bin/avrdude -CC:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf -v -patmega2560 -cwiring -PCOM3 -b115200 -D -Uflash:w:C:\Users\maxwe\AppData\Local\Temp\build5293bcfb34d481e68504cd52e8acbf99.tmp/ROBO3DR1PLUSV2.ino.hex:i

avrdude: Version 6.0.1, compiled on Apr 15 2015 at 19:59:58
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2009 Joerg Wunsch

System wide configuration file is "C:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf"

Using Port : COM3
Using Programmer : wiring
Overriding Baud Rate : 115200
avrdude: ser_open(): can't open device "\.\COM3": Access is denied.

avrdude: ser_drain(): read error: The handle is invalid.

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"
option enabled in File -> Preferences.

I have the same problem :frowning:
I don’t know how to fix that.

Make sure that no other program running on your computer has COM3 open. The culprit is likely the software used to control your 3D printer.

If you have verified that no other program has the port open, then try restarting your computer. Sometimes COM ports will get stuck open and the restart fixes that.