Unable to Open Connection to Com1: 8 Ways to Fix

Driver updates are a vital fix which can help with this issue

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Key notes

  • 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.
  • In most cases, reinstallation or updates of your drivers should resolve this problem. 

If you are unable to open a serial port, you are in good company, and in this guide, we will be telling you all you should know.

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

By the end of this article, you should have successfully fixed all problems with your serial port. Some of the solutions may be relevant to COM ports on Windows.

Why is serial port not working?

Here are the top reasons you should have in mind:

  • Incorrect communication settings – For the devices to work together correctly, they must be configured with the same communication settings.
  • Wrong serial cable – If you use the incorrect serial cable, you will be unable to connect.
  • Software conflicts – A software driver might make a serial port unusable. This driver can stop working if it is improperly installed or incompatible with a serial port.
  • Faulty wiring – This may cause issues when a control system is connected to a device.

Some variations of serial port problems that users have faced include:

  • Unable to open serial port access is denied – In most cases, Access Denied occurs when another program is utilizing the port.
  • Failed to open serial port Betaflight – Though it’s not a true USB interface, the flight controller communicates with your computer through a USB connection.
  • COM port not detected Windows 10 – Your PC will display the warning unable to open serial port if the COM port isn’t recognized.
  • Unable to open connection to com1 – This problem may sometimes arise if you don’t have the proper drivers.
  • 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 10 – Sometimes, 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.

Now, let us show you how to resolve this error on your Windows PC.

How do I fix unable to open serial port?

1. Make sure that you have the necessary drivers

  1. Right-click the Start menu and select Device Manager.
    unable to open serial port
  2. Expand the Universal Serial Bus controller category.
  3. Right-click on your driver and choose Update driver.
  4. Lastly, click on Search automatically for drivers.

If you’re getting the Unable to open serial port message, perhaps the problem is related to your drivers. To fix this issue, we recommend updating your serial port driver.

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

Outbyte Driver Updater will provide a detailed report of all of your current and obsolete device drivers. In addition, it updates the most recent device drivers from the complete database regularly.

Outbyte Driver Updater is the best choice when updating all your drivers automatically, with just a couple of clicks.

It will keep your computer safe from downloading and installing the wrong driver version, which can cause severe malfunctions and ease the process.

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

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

try to disconnect the cable

This is a simple workaround, but several users reported 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 that when they were unable to open a serial port while trying to use the serial port, it turned out that the problem was the Windows Fax and Scan service.

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

Remember that this is just a workaround, so you might have to repeat it whenever you want to use a serial port on your PC.

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.
  4. Wait for a couple of moments, and then enable the serial port.

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

A temporary glitch usually causes this, and to fix the problem; we recommend disabling the serial port temporarily.

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

5. Try using a different cable

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

try a different cable

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

6. Restart the device

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

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.

Sometimes, an 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 relatively straightforward in Windows 10, and for the most part, Windows installs the updates on its own. Once your system is updated, check if the problem is still there.

How to enable COM port in Windows 10?

  1. Click the Windows key, enter regedit and select the Registry Editor app.
  2. Navigate to the part below:
  3. On the right pane, double-click on Start.
    unable to open serial port
  4. Change the Value data to 4 and click OK.
    unable to open serial port

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.

Remember that we have not made these solutions in any particular order, so you should try what seems most appropriate for your situation.

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

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