How to Fix the ‘Connection Problem or Invalid MMI Code’ Error in Android (2024)

Mobile Phones > Android

Man-Machine Interface codes, or MMI codes, are specific series of numbers and symbols that perform functions or retrieve information. For example, use ##232339## to perform a Wi-Fi network test. MMI codes don’t work all of the time, however; this article covers all of the best ways to fix invalid code MMI warnings and stop them from happening again in the future.

How to Fix Android Invalid MMI Code Errors

Here are all of the most effective ways to fix an invalid code MMI error warning and prevent it from happening again. It’s best to work through these in the order presented, as we've sorted them from the easiest and simplest to most complex.

1. Double-check the MMI code. Make sure that you entered the MMI code correctly.

2. Check the MMI code compatibility. Your smartphone’s manufacturer and your mobile provider’s websites should have a full list of compatible MMI codes for your Android. The manual that came with your smartphone may also have a list of approved codes.

3. Restart your Android smartphone. A basic restart could fix whatever issue is causing the errors.

4. Update the Android operating system. A system update often includes a lot of bug fixes in addition to the latest features and security updates.

5. Turn Airplane Mode on and off. Quickly reset your smartphone’s connection to its mobile network and the internet by turning on Airplane Mode, waiting several seconds, and then turning it off again.

6. Change the cellular network connection. Switching between 5G to 4G or even 3G or LTE could help the MMI code work.

7. Disable one SIM card. If you use a Dual-SIM Android smartphone, open Settings and select Connections > SIM card manager. Turn the switch next to one of the SIM cards off, and then try again. If the code doesn’t work, reactivate the SIM card, turn the other one off, and then repeat the code.
   

   Once you’re done with this test, make sure to turn both SIM cards back on again.

8. Check the SIM card. Safely remove the SIM card, inspect it, and reinsert it. Removing and reinserting the SIM can reset the phone’s connection to the card and possibly realign it. If you notice dirt or dust build-up around the SIM card tray, give it a quick clean with a microfiber cloth or airgun before you reinsert the SIM.
   

   If your SIM card appears burnt or severely damaged, have it checked by an expert at your nearest carrier’s office.

9. Clear the Android's cache. Clearing the cache can get rid of MMI error messages and improve overall device functionality.

10. Update all of your Android apps. An app could be causing system conflicts and may need an update to fix this issue.

11. Run Android in Safe Mode. Restart your Android mobile in Safe Mode and then attempt the MMI code that’s been giving you the error message. If the code works, then the problem is an app conflict of some kind. If the code doesn’t work, then the issue is likely hardware or network-related.

12. Uninstall problematic Android apps. If the MMI code worked fine in Safe Mode, a recently installed app is likely causing the problem. You may also want to take this opportunity to remove old apps that you no longer use. Perform a basic restart after you’ve finished uninstalling all of the apps you want to get rid of.

13. Reset your Android smartphone’s network settings. Clearing your device’s network settings is a common fix for several connectivity glitches, including recurring invalid MMI code error messages.

14. Add a comma to override the command. Adding a comma to the end of an MMI code will bypass any error message and force the code to process. For example, *#3282# becomes *#3282#,.

    Adding a comma is a good workaround when you can’t work out the cause of the error messages or can't do any of the above fixes due to more serious hardware or software problems.

15. Factory reset your Android. As an absolute last resort, you can return your Android smartphone to its as-new state. This process will likely fix any software conflicts, but it will also remove the majority of your data and settings from the device. Make sure to perform a backup first.

What Causes ‘Invalid MMI Code’ Errors?

An MMI invalid code error is typically due to one or more of the following hardware or network issues.

• SIM card conflict. Dual-SIM Android smartphones often get MMI code errors.
• A damaged or dirty SIM card. Anything that prevents the SIM card from being read correctly can trigger an invalid MMI error.
• Phone network connectivity issues. Difficulty in connecting to the network can prevent a code from being processed.
• Using the wrong MMI code. The code may have been entered incorrectly or isn’t compatible with your handset or network.
• Third-party apps. Some apps that didn’t come pre-installed on your Android mobile can prevent MMI codes from working.