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What does invalid MMI code mean? How to fix it?

When a robot performs a task, human beings and computers may be able to work together. But what happens if a computer performs a task that a human being is better suited for? Or if a human being performs a task that a robot is better suited for? This question has led to the development of the Man-Machine Interference (MMI) code.

A Man-Machine Interface code or MMI code is a cellphone code. This code usually begins with the prefix *# (star/hash). The primary purpose of these codes is to extract and obtain information and enable and disable different functions or actions.

There may be multiple reasons why the “Invalid MMI code” error may occur. Generally, issues with the carrier provider or the SIM authentication lead to the error. We’ve laid out five quick fixes for the error “Invalid MMI code” in this article.

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Restart/Reboot the device

The most traditional and probably the first fix everyone tries is rebooting the device. It’s a straightforward fix but works wonders very often. Hold down the power button, and select the Restart option from the menu.

If you wish to troubleshoot your device better, try rebooting it in safe mode. This will eliminate all the other applications running in the background, and the invalid MMI code issue can be appropriately tested.

The safe mode disables all the pre-installed services and applications. You can reboot in safe mode in the following manner:

  • Turn off the device.
  • Hold the power button down to turn on the device, and do not release it until the logo appears on the screen. Once the logo appears on the screen, release the power button.
  • Hold down the volume down button till the reboot is completed.
  • On the bottom left of the screen, Safe mode should be displayed.

The buttons may vary for a few models; check the phone manual. Once in the safe mode, enter the MMI used and verify if the error still exists.

If there are no issues in sending text messages, then there is an issue caused by some application. Start with checking the most recently installed application, after which the error for the MMI code was persistent.


Network settings

MMI code issues are interrelated with the network settings in every way. While the process to access the network settings may differ from phone to phone, the basic steps remain the same –

What does invalid MMI code mean? 5 quick fixes
  • Open the Settings.
  • Go to the Network Connection option.
  • Select the Mobile Networks option.
  • Open Network Operators and then select Wireless provider from the search.
  • Try connecting and reconnecting 3-4 times till it starts functioning again.

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Aeroplane mode

Another very common fix for errors occurring on phones. Since the MMI code error may occur due to weak signal strength, resetting the connection can help fix the error.

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  • Go to the setting and turn On the Airplane mode.
  • Wait for about 30 seconds to a minute, and then turn Off the Airplane mode.

Resetting the network may resolve the error.


Modification of the MMI code

Another method to fix the error for the Invalid MMI code is the addition of a comma at the end of the prefix code. Adding the comma at the end forces the required operation to execute and overlook all the errors.

A comma can be added by holding the asterisk key for 3-5 seconds.

What does invalid MMI code mean? 5 quick fixes
Original MMI code (Left), MMI code with a comma (Center), MMI code with plus (Right)

Similarly, adding a plus sign after the asterisk sign in the code forces the operation to look for the Invalid MMI code error and get rid of the error message, allowing the call to get through.

Through this process, the operation is forced to look for the USSD code errors. The plus sign can be added by holding the zero key for 3-5 seconds.


Check SIM card

Having more than one SIM card may cause the error since both the SIMs are probably running together. Disable all the SIM cards, except the one for sending the MMI code, and verify the working.

Moreover, under the dual SIM settings of the phone, select the option, Always ask, so that the phone will prompt every time regarding the SIM you want to use for failing the MMI code. If the phone has only one SIM, try removing it, cleaning the slot and card, and inserting it again to establish the connection.

Also read: Your SIM sent a text message: What does it mean and how to stop it?

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