How to fix a Galaxy S9 Plus that won’t unlock screen with correct passcode all the time

We’ve recently received anecdotal accounts from some #GalaxyS9 and #GalaxyS9Plus owners about their device being unable to consistently unlock screens using a correct passcode. Toda’ys troubleshooting article should provide the solutions for this issue.

Today’s problem: Galaxy S9 Plus won’t take PIN all the time

Dear Droid Guy, thank you very much for posting so many helpful articles. I used your article when my S7 was acting out and it helped. However, with my new Samsung S9+ nothing is working 🙁

First of all the PIN I set with the new device does not work all the time. It is very weird. I set the Pin to 0000 to make sure it’s not my mistake. The first time I tried 0000 it said Pin wrong! The second time I tried it worked! When I traveled to Paris the phone was acting out completely. First of all it was restarting like crazy. So bad I could not use it anymore. It even restarted in flight mode. I went to the samsung support center. They said they could not find any mistakes, but the phone is still acting out. I messaged their support team. They told me its my network! I don’t understand what Pin has to do with my carrier. We used my boyfriend’s sim as well but it had the same problem. I really don’t know what to do anymore T_T Sorry I don’t know the Android Version. It restarted and I have not set it up yet. Kind Regards. — Jana Chen.jana.at

Solution:Hi Jana. If by PIN you mean to say the passcode to unlock the screen, then you and Samsung were actually not on the same level. Normally, when you say PIN, it refers to the number that you enter to secure a SIM card. We think this is why Samsung told you that there might be an issue with your carrier.

Based on how you describe the issue, there’s high likelihood that it’s being caused by a software glitch. This troubleshooting article should help you fix this software problem. Below are the solutions that you can do:

Solution #1: Clear the cache partition

Android uses a special set of cache called system cache to work efficiently. Specifically, it utilizes the system cache, stored in the cache partition, in order to load app quickly. Sometimes, this cache gets corrupted, which can result to all sorts of issues. Ideally, Samsung users should regularly clear the cache partition in order to force their devices to build a new cache. Since this seldom occurs, performance issues and other weird issues sometimes occur. To see if your S9 Plus is having an issue with its cache partition, make sure that you clear it first. Here’s how:

  1. Turn off the device.
  2. Press and hold the Volume Up key and the Bixby key, then press and hold the Power key.
  3. When the Android logo displays, release all three keys.
  4. An ‘Installing system update’ message will show for 30 – 60 seconds before the Android system recovery menu options appear.
  5. Press the Volume down key several times to highlight wipe cache partition.
  6. Press Power key to select.
  7. Press the Volume down key to highlight yes, them and press the Power key to select.
  8. When the wipe cache partition is complete, Reboot system now is highlighted.
  9. Press the Power key to restart the device.
  10. Check if the problem returns. If it doesn’t then it was definitely a cache issue. If the issue remains though, you should continue with the troubleshooting below.

Solution #2:  Reset settings

Should wiping the cache partition won’t fix the issue, your next troubleshooting step is to see to it that your S9’s settings are reset to defaults. There’s a chance that your issue may be caused by a misconfiguration of one or more Android settings so in order to effect a broad change to the entire system, reset everything must be performed. Unlike a factory reset, this type of reset won’t delete your personal data so they should be safe. Still we want you to back your phone up before doing this reset to be sure.

  1. Open Settings app.
  2. Tap General management.
  3. Tap Reset.
  4. Tap Reset settings..
  5. Tap RESET SETTINGS button.
  6. Restart your S9 and check if the issue is gone.

Solution #3: Reset app preferences

Other users were able to fix basic Samsung issues and feature-specific problems by ensuring that all apps are set up properly. If you are the type who tend to tweak some settings or app settings and forget about it, you’ll most likely encounter “abnormal” Android behavior from time to time. To ensure that you enable all necessary system apps and services, you can reset your app preferences by doing the steps below:

  1. Open Settings app.
  2. Tap Apps.
  3. Tap More settings at the upper-right hand side (three-dot icon).
  4. Tap Reset app preferences.
  5. Tap Reset to confirm.

Reset app preferences will re-enable previously disabled apps, blocked app notifications, nominated app permissions, among others.

Solution #4: Boot to safe mode and observe

The most likely reason for the problem is a third party app. Poorly-coded or incompatible apps are usually the cause why Android features malfunction or stop working altogether. To see if our suspicion is right, restart your S9 Plus to safe mode first. After that, let the phone run for at least 24 hours. Make sure that you don’t restart it in order not to revert it normal boot mode. If your S9’s screen passcode works normally throughout the observation period of 24 hours, that’s a clear indication that one of the apps is problematic.

While safe mode is active, no third party apps will be allowed to run so you won’t be able to use some of your favorite apps. You should still be able to send and receive SMS and make and receive calls.

To restart your S9 to safe mode, follow these steps:

  1. Turn the device off.
  2. Press and hold the Power key past the model name screen appearing on the 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. When Safe mode appears in the bottom left corner of the screen, release the Volume down key.
  7. While in Safe mode, you can now uninstall apps that are causing a problem.

Related reading: How to reboot your Samsung Galaxy S9 in Safe mode and uninstall problematic apps (easy steps)

Solution #5: Factory reset

Finally, you should not hesitate to factory reset your device if the problem remains. Ideally, any of the solutions above should be able to deal with your issues. If they remain, especially when your S9 is on safe mode, factory reset should help.

To factory reset your S9:

  1. From the Home screen, swipe up on an empty spot to open the Apps tray.
  2. Tap Settings > Cloud and accounts > Backup and restore.
  3. Tap the following sliders to desired setting: Back up my data, Automatic restore.
  4. Tap the Back key (bottom right) until you reach the main Settings menu.
  5. Tap General Management > Reset > Factory data reset.
  6. Scroll to the bottom of the screen, then tap RESET > DELETE ALL.
  7. If you have screen lock turned on, enter your credentials.
  8. If prompted to verify your Samsung account, enter the password, then tap CONFIRM.
  9. Wait for the device to finish the reset sequence.

Remember, factory reset will wipe your personal data. Be sure to back them before doing a factory reset.


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