FIX: Unable to open serial port

Milan Stanojevic
by Milan Stanojevic
Deputy Editor
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  • Serial ports are the interface between a PC and devices that don't support a Bluetooth connection.
  • Driver errors or physical damage can cause your serial ports to become unresponsive. We've got some quick tips for that.
  • To keep you safe, also take your time to check out the best software tools for blocking USB ports.
  • This detailed article is part of our Windows 10 Errors Hub, so do not hesitate to bookmark it.
Fix Unable to open serial port

A serial port can be useful, but some users reported Unable to open serial port error messages on their PC. This can be a big problem, and in today’s article, we’ll show you how to fix this error.

Problems with a serial port can be quite annoying, especially if you tend to use the serial port frequently.

How do I fix a serial port that doesn’t open in Windows 10?

  1. Make sure that you have the necessary drivers
  2. Verify that the port isn’t open/disconnect the cable
  3. Stop the Windows Fax and Scan service
  4. Disable the serial port in Device Manager
  5. Try using a different cable
  6. Restart the device
  7. Reinstall the serial port driver
  8. Make sure that the system is up to date

1. Make sure that you have the necessary drivers

If you’re getting the Unable to open serial port message, perhaps the problem is related to your drivers. To fix this issue, it’s advised to update your serial port driver.

To do that, you can visit your motherboard manufacturer’s website and download the latest drivers. If you find this process a bit tedious or complex, you can always use a third-party tool.

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2. Verify that the port isn’t open/disconnect the cable

try to disconnect the cable

Sometimes Unable to open serial port message can appear if the port is already open. To fix this problem, users are suggesting to disconnect the cable from the other device and try to connect again.

This is a simple workaround, but several users reported that it worked for them, so feel free to try it out.


3. Stop the Windows Fax and Scan service

  1. Press Windows Key + R keyboard shortcut to open the Run dialog.
  2. Enter services.msc and press Enter or click OK.
    services run window can't open serial port
  3. When the Services window opens, locate Windows Fax and Scan service and double-click it to open its properties.
    • If this service isn’t available, try changing the settings of the Fax service.
  4. Set the Startup type to Manual and click the Stop button to stop the service. Now click Apply and OK to save changes.
    manual startup type serial port not working

Several users reported Unable to open serial port message while trying to use the serial port. It turns out that the problem was Windows Fax and Scan service.

To fix this problem, you just need to stop Windows Fax and Scan service. After doing that, check if the problem is still there.

Bear in mind that this is just a workaround, so you might have to repeat it every time you want to use a serial port on your PC.


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4. Disable the serial port in Device Manager

  1. Press Windows Key + X and choose Device Manager from the list.
    serial port device manager
  2. When Device Manager opens, locate the serial port, right-click it, and choose Disable device from the menu.
  3. When the confirmation dialog appears, click Yes.
    disable device serial port can't open
  4. Wait for a couple of moments and then enable the serial port.

If you keep getting Unable to open serial port message on your PC, the issue might be related to the serial port driver.

This is usually caused by a temporary glitch, and in order to fix the problem, it’s advised to disable the serial port temporarily.

After doing that, check if the problem is resolved. If this solution works for you, bear in mind that you’ll have to repeat it every time you want to use your serial port.


5. Try using a different cable

try a different cable

Sometimes, the Unable to open serial port error can appear if your USB cable isn’t working. Be sure to check if your cable is properly connected. In addition, check for any visible damage.

If your cable seems to be in order, try replacing it and check if the problem appears with a different cable.


6. Restart the device

try to restart the device

If Unable to open serial port keeps appearing, perhaps you can fix the problem by restarting your devices.

Simply restart the device you’re trying to connect to and check if that solves the problem. Alternatively, you can restart your PC and see if that solves the issue.


7. Reinstall the serial port driver

  1. Open Device Manager.
  2. Locate your serial port, right-click it, and choose Uninstall device.
    uninstall device serial port can't open
  3. Now click Uninstall to confirm.
    confirm device uninstall serial port not working
  4. Once the device is uninstalled, restart your PC.

As we already mentioned, sometimes issues with your serial port can be caused by your drivers.

If you keep getting Unable to open serial port message, you might be able to fix the problem simply by reinstalling the serial port driver.

After your computer restarts, Windows should install the default driver and the problem will be completely resolved.


8. Make sure that the system is up to date

  1. Open the Settings app and go to the Update & Security section.
  2. Now click the Check for updates button in the right pane.
    update windows open serial port
  3. If any updates are available, they will be downloaded automatically in the background and installed as soon as you restart your PC.

In some cases Unable to open serial port message can appear if your system isn’t out of date.

An outdated system can lead to various compatibility issues, and the best way to avoid these issues is to update your system.

This process is quite straightforward in Windows 10, and for the most part, Windows installs the updates on its own. Once your system is up to date, check if the problem is still there.


If you’re having trouble opening the Setting app, take a look at this article to solve the issue.


Getting the Unable to open serial port message can be a problem for many users that use the serial port frequently, but you should be able to fix this problem using one of our solutions.

Speaking of these kinds of problems, here are some related issues that users reported:

  • Unable to open a connection to com1 Windows 10, com3 – This issue can sometimes appear if you don’t have the necessary drivers. To fix it, be sure to update the serial port driver and check if that solves your problem.
  • Putty unable to open serial port Windows 10Sometimes, this issue can occur due to certain Windows services. This isn’t a major problem, and you can fix it by disabling those services.
  • Unable to open serial port com1 access is denied – This issue can appear due to glitches with a serial port. Temporarily disable the serial port and check if that helps.
  • Unable to open com port win error code 5, 123, 3 – These are some common problems that can appear with a serial port, but you should be able to fix most of them with one of our above tips.

Let us know which one worked for you in the comments area below.

FAQ: Learn more about serial ports

  • What is a serial port?

A serial port is a serial communication interface that allows sequential information transfers.

If you encounter issues using them, check out this detailed article for more information.

  • Is a USB port a serial port?

Yes, as long as the port can be used to read and write data from and to another device, it can be considered a serial port.

  • What can I connect using serial ports?

A serial port can be used to connect a PC to pretty much any other type of peripherals, such as mice, keyboards, monitors, projectors, and more.

Editor’s Note: This post was originally published in April 2020 and has been since revamped and updated in September 2020 for freshness, accuracy, and comprehensiveness.

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