How to fix a Galaxy S9 that reboots on its own during calls

As promised, here’s another troubleshooting article for the Galaxy S9 (#GalaxyS9). We are now getting so many S9 issues daily so it can take us some time to address all of them. In the meantime, here are some of the common problems that a lot of S9 users encounter. We include three cases in this post so hopefully you’ll find it helpful.

If you are looking for solutions to your own #Android issue, you can contact us by using the link provided at the bottom of this page. When describing your issue, please be as detailed as possible so we can easily pinpoint a relevant solution. If you can, kindly include the exact error messages you are getting to give us an idea where to start. If you have already tried some troubleshooting steps before emailing us, make sure to mention them so we can skip them in our answers.

Problem #1: How to fix a Galaxy S9 that reboots on its own during calls

Phone dies sometimes with nearly full battery and no warning. Instant black screen. Failure only accurs when receiving incoming call. None of the hard reboot (down volume and power for 30+ seconds, remove sd card, etc…) will cause phone to power up. Phone always powers up within 5 seconds of plugging it in.  Circular charge indicator appears, and circumference of circle lights up indicating battery power in excess of 80%. Phone will then turn on and operate normally until next event. Event was rare, but is happening with greater frequency. Phone was under water (about 2 feet for 30 seconds) months before this error ever occurred. Android version I submitted is my best guess.

Solution: Your phone’s battery may need calibrating. The description of your situation is sometimes a manifestation that the operating system may not be getting the true battery readings. This leads to premature shut downs like what you’re experiencing.

How to calibrate Galaxy S9 battery and OS:

  1. Drain the battery completely. This means using your device until it powers down by its own and the battery level reads 0%.
  2. Charge the phone until it reaches 100%. Be sure to use original charging equipment for your device and let it charge up completely. Do not unplug your device for at least two more hours and also don’t use it while charging.
  3. After the elapsed time, unplug your device.
  4. Restart the device.
  5. Use your phone until it completely runs out of power again.
  6. Repeat steps 1-5.

Install updates

If the problem returns after recalibrating, there may be other reasons for your case. The next troubleshooting you want to do is to ensure that all apps are up-to-date. If you have apps from outside the Play Store, be sure to update them as well.

It also goes without saying that you need to update Android if there’s any available update for it.

Wipe the phone

The last software troubleshooting that you can do in this case is factory reset. Doing so will ensure that all software settings are returned to their defaults. If the reason for the problem is a software bug, factory reset will most likely help.

Below are the steps to factory reset your S9:

  1. Create a backup of your personal data.
  2. Turn off the device. This is important. If you can’t turn it off, you’ll never be able to boot to Recovery Mode. If you are not able to shut the device off regularly via the Power button, wait until the phone’s battery is drained. Then, charge the phone for 30 minutes before booting to Recovery Mode.
  3. Press and hold the Volume Up key and the Bixby key, then press and hold the Power key.
  4. When the green Android logo displays, release all keys (‘Installing system update’ will show for about 30 – 60 seconds before showing the Android system recovery menu options).
  5. Press the Volume down key several times to highlight ‘wipe data / factory reset’.
  6. Press Power button to select.
  7. Press the Volume down key until ‘Yes — delete all user data’ is highlighted.
  8. Press Power button to select and start the master reset.
  9. When the master reset is complete, ‘Reboot system now’ is highlighted.
  10. Press the Power key to restart the device.

Contact Samsung

As an end user, there’s only so much that you can do to fix an issue like this. Your Galaxy S9 is a complicated blend of hardware and software and there are way too many variables to identify what may be causing it to reboot during calls. If factory reset won’t do a thing, we suggest that you ask Samsung for help.

Problem #2: Galaxy S9 Plus signals become weak after update

Hi. I have the Samsung S9 Plus. I’ve been having issues ever since I got the latest update from Oreo. My internet seems to not be functioning correctly. the signals are very weak. I have removed the SIM card, I have rebooted my phone, I’ll even got to the point I had to do a factory reset. nothing has been able to resolve my issue.

I’ve contacted Sprint to have them troubleshoot. they couldn’t do much to fix the issue either so they sent me into the store so a technician can do a Hands-On. he couldn’t do anything either. they stated since the last update I got which was Oreo my phones internet seems to have slowed down really bad. I’ve been struggling with the internet signal since September 20 something. I know it’s not the location because I have friends that have Sprint and their internet is working perfectly fine but then yet they don’t have a Samsung S9 plus they have the note 9. please help me.

Solution: Mobile or cellular data connection depends on a number of basic things to work as expected. For one, the device must be in a location with good cellular coverage. In other words, it should have a minimum of 3 signal bars all the time. If your S9 has 2 or less signal bars, that can be the reason why mobile data speed is slow. It can be caused by poor service in that area, or a modem firmware bug in your phone. Try to visit an area where your S9 can get full signal bars and compare the mobile data speed. If it works as expected, the most likely reason is poor service and not a device issue.

If your S9 Plus continues to have slow mobile data speed in areas with full network bars, there may be something in your phone that causes it. It can be an app that runs in the background and running network tasks. In this case, try to boot the phone to safe mode and observe the speed. In safe mode, no third party apps will be running. If the speed improves in safe mode but not in normal mode, then you have a bad app problem. To boot to safe mode:

  1. Turn the device off.
  2. Press and hold the Power key past the model name screen.
  3. When “SAMSUNG” appears on the screen, release the Power key.
  4. Immediately after releasing the Power key, press and hold the Volume down key.
  5. Continue to hold the Volume down key until the device finishes restarting.
  6. Safe mode will display in the bottom left corner of the screen.
  7. Release the Volume down key when you see Safe Mode.

If you think there’s an app issue, you can use the method of elimination to pinpoint the app. It’s not easy though, especially if you have plenty of apps to work from. To identify which of your apps is causing the trouble, you should boot the phone back to safe mode and follow these steps:

  1. Boot to safe mode.
  2. Check for the problem.
  3. Once you’ve confirmed that a third party app is to blame, you can start uninstalling apps individually. We suggest that you begin with the most recent ones you added.
  4. After you uninstall an app, restart the phone to normal mode and check for the problem.
  5. If your S9 is still problematic, repeat steps 1-4.

Problem #3: Galaxy S9 won’t charge

Hello. I have a Samsung Galaxy S9. The issue I am currently experiencing is that I am unable to charge it. I didn’t have the issues until about an hour ago and it is become very frustrating. I literally talked on the phone and then put it on the charger to charge but, it didn’t. I have been very observant and taken notes on everything. I have tried using different outlets, changing cords, factory resetting the phone (rebooting it didn’t help since the phone never turned on but, flashed the Samsung logo for 10 minutes), and even plugging it in to my computer and nothing has worked. My phone is still on 0%, the LED doesn’t turn on red, and the battery doesn’t come on to let me know that it is charging properly. I did however plug the phone up to my computer and it made a noise as if it connected and the battery signed flashed for a second then it cut off. My computer then popped up a message stated that the “connection malfunctioned”. Unsure of what that may be. 

Solution: There may be a problem with your phone’s charging port. If factory reset did not make a difference, then the cause is not software in nature at all. You should have the phone checked by a professional so proper hardware tests can be done. In the meantime, you can try to charge your phone wirelessly to turn it back on and allow you to create a backup of your personal data.


If you are one of the users who encounters a problem with your device, let us know. We offer solutions for Android-related problems for free so if you have an issue with your Android device, simply fill in the short questionnaire in this link and we will try to publish our answers in the next posts. We cannot guarantee a quick response so if your issue is time sensitive, please find another way to resolve your problem.

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