Android How to

How to Fix Invalid MMI Code or Connection Problem

MMI code
Written by Kelly Houstan

It is really common for Android users in order to face a connection problem as well as an invalid MMI code on their devices each and every so often. This can be really annoying since it simply means that you guys won’t be able to send any text messages. As well as make any calls until this error is fixed as well. Just read this article to know all about How to Fix Invalid MMI code or Connection problem. Let’s start!

The MMI code, also known as the Man-Machine Interface code is a really complex combination of digits and alphabetical characters.  That you guys enter on your dial pad along with the * (asterisk) and # (hash). In order to send a request to the providers to check the account balance, activating as well as deactivating the services, etc. This MMI code error basically occurs due to many reasons. Such as SIM authentication issues, also weak carrier providers, wrong position of the characters, as well.

In order to solve this issue, we have jotted down a list of ways to fix the connection problems or the invalid MMI code. So, let’s now start!

How to Fix Invalid MMI Code or Connection Problem

Try rebooting to the safe mode

This step will now cut off all the third-party apps as well as any external software running in the background disturbing your phone’s functioning as well. It will also help your device in order to troubleshoot the issue along with only running the stock Android programs. Also, it is really simple and easy to do this trick as well.

Steps to turn on the safe mode, have a look:

  • Tap & hold the power button of your device.
  • Now from the options, just click on Restart.
  • On your display, you guys will see a pop-up asking you if you want to Reboot to safe mode, and then click on OK.
  • Your phone will also be booted to the safe mode now.
  • Also, you’d be able to see the safe mode that is written at the bottom-left corner of your home screen.

Activate the radio and SMS over IMS

Turning on the SMS over IMS and then activating the radio can also help out in fixing this issue as well. Also, you can perform the following steps in order to do so:

  • You can open your dial pad and type *#*#4636#*#*. You don’t necessarily have to tap on the send button as it will automatically flash the service mode.
  • Click on service mode and then tap on either Device information or Phone information.
  • Tap on the Run Ping test button and then choose the Turn Radio Off button.
  • Choose Turn on SMS over the IMS option.
  • Now, you guys just have to simply reboot your device.

Make changes in the prefix code

You can just simply fix the connection Problem or the invalid MMI code on your device via modifying and changing the prefix code. All you guys have to do is put a comma at the end of the prefix code. Adding a comma will also force the operator in order to overlook any error and then perform the task.

We have now listed down two different ways in order to do so:


Supposedly, the prefix code is actually *3434*7#. Now, just put a comma at the end of the code, i.e.*3434*7#,

MMI Code


Rather, you guys can add the + symbol after the * sign i.e. *+3434*7#

Restart your device

Just simply reboot your device and hope for better results. Most of the time this trick resolves all the common issues. The steps in order to reboot/restart your phone are as follows:

  • Just long-press the power button. In many cases, you may need to press the volume down + home button until a menu pops up. It is not important to unlock your phone to do this process.
  • Now, choose the restart/reboot option among the list, and then just wait for your phone to restart.

Check whenever the code error is still occurring.

Check your SIM card | MMI code

Well, if nothing really works, then take a look at your SIM card, maybe it is also the one creating problems. Mostly, your SIM card is damaged due to continuous pulling out and reinsertion. Or, maybe it was just cut roughly. Whatever the reason may be, your SIM card is now probably corrupt. We recommend you change and get a new SIM card in this kind of situation before it is too late.

Also, for the ones using a dual SIM smartphone, you need to choose between the two:


Just deactivate one of the SIM cards and turn on the one that you’re using to send the MMI code. Many times your phone may not use the correct SIM card if you guys have both of them performing together.


  • Head to the Settings and find SIM cards and mobile networks.
  • Also, find the phone’s dual SIM settings and then click on the Voice call Settings.
  • A pop-up list will appear, that is asking you to select between Always Use SIM 1, SIM 2, or Ask every time.
  • Choose the Always Ask option. Now, whenever dialing the MMI code, your phone will then ask you which SIM you want to use. Choose the correct one for proper results.

If you guys own a single SIM card device, then try pulling out and reinserting your SIM card after cleaning and blowing on it. Just see if this trick works or not.

Keep a check on network settings | MMI code

You guys might want to check your network settings if your signal is weak and unstable as well. Your phone longs for a better signal due to which it tends to shift constantly between 3G, 4G, and EDGE, as well. So, a little tweaking here and there will hopefully fix your issue. Following are the steps to do that:

  • Head to the Settings.
  • Now navigate to Network Connection and click on it
  • Then, click on the Mobile networks option and just look for the Network operators.
  • At last, search the network operators and click on your Wireless provider.
  • Now repeat this process another 2-3 times.
  • Reboot/restart your device and now hopefully, it will start working again.


Well, That is all from my side. If you want to know more about this article or have any queries. Then feel free to ask me anything in the comments section below.

Have a Good Day!

Also See: How to Fix Instagram Not Posted Yet Try Again

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Kelly Houstan

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