How To Repair ‘Connection Problem or Invalid MMI Code’


By Jason

Update on

connection problem or invalid MMI code

A very common issue in phones is a connection problem or invalid MMI code.

This issue frequently occurs on the Samsung Galaxy series, which has a dual SIM card feature, or smartphones that allow 2 SIM cards from 2 unique networks at a similar time compared to the rest of the phone brands.

Well, there must be some people who don’t know about the MMI code. This code is the one that we type in the device, and these codes include some special characters, such as ‘#’ and ‘*.’

The connection problem or invalid MMI code is a well-known error that usually occurs because of no or poor network connection.

And because of this issue, a lot of people are unable to place calls or receive them. Moreover, they are not able to send messages also.

So, before getting into the solutions to repair connection problems or invalid MMI codes, we should know about MMI codes. Other than this, it is necessary to understand the working of MMI codes too.

Now, without any further ado, let’s get into the article. Hopefully, this article will solve your doubts about MMI codes as well as how to repair connection problems or invalid MMI codes.

Part 1: Define MMI Codes?

Man-Machine Codes or MMI Codes, are the special codes that you dial on the keypad of the phone. MMI codes are dialed on the keypad to communicate with the SIM, phone, or with the service provider’s network operator PCs.

With the help of MMI codes, you can get access to valuable information or change SIM/phone settings that you can access via your smartphone’s UI (User Interface).

MMI codes comprise of special characters like an asterisk (*) and hash (#). The common MMI code to have communication with the phone is ‘*#06#8*.’ This code is used to obtain the phone’s Serial/IMEI number.

A different set of MMI codes is the USSD codes. These codes are also called Feature codes or Quick codes. USSD codes are generally used in GSM cellular telephones in order to converse with their specific mobile network operators. Also, most people frequently use USSD codes to see their prepaid balance.

The very famous problem that is seen is the connection problem or invalid MMI code. Other than this, the message can also state that the MMI code that you have entered is causing the error.

Otherwise, the code is being entered via a device that has 2 active connections. Therefore, it is advisable to stop the usage of the SIM that you are not using. Only keep one SIM active and then try to enter the MMI code.

So, this was all about the MMI codes. We hope that you are clear about the definition of MMI codes. Now, let’s move ahead with the working of these codes.

Part 2: Working of MMI Codes

In this section, we will brief you about the working of the MMI codes. When you type an MMI code on the dialer, it is further processed to the phone’s MMI reader. In case the MMI code is not identified, then it is transmitted to the network verbatim.

For instance, you sent a specific code, such as *09876*54321#. Now, the MMI parser of the phone will transmit the ‘command’ to your phone. If the code is not identified as an internal command, the code will be sent to the network operator verbatim.

Every network has a particular set of MMI codes, which they utilize for their own. In case you get a message stating ‘connection problem or invalid MMI code,’ it is an indication that the specific code has not been identified or your phone is not able to connect to the network.

Since now we all are aware of the working of the MMI codes, let’s study how to solve the connection problem or MMI code issue. So, if you wish to know some best solutions to repair this issue, then do not skip the next part.

PS: Should you have problems with SIM network unlock PIN, click to switch.

Part 3: Solutions to Repair Connection Problems or Invalid MMI Code

This part will brief you about the five best solutions to repair the connection problem or invalid MMI code issue. Hopefully, this will solve the issue easily without much hassle.

1. Analyze the Code That You Wish to Use. Add Some Extra Special Characters.

Try to add a comma (,) at the finish of the MMI code before sending the code. The comma as an extra character will prompt your smartphone to deal with different errors on your phone and transmit to the specific network.

Have a look at this example:

If the code is *3457*9# and it displays an error, then dial this code with an extra comma at the end. We will show you how ‘*3457*9#,’

In case the added comma does not work, insert ‘+‘ after the ‘*‘ and at the beginning of the 1st digit. The thing is this code will function when the 1st character of the code begins with ‘*’ (asterisk). For instance, *+3457*9#

The (+) plus sign will inform the phone to force the process of execution and see the phone errors that might come in the way.

Try using this method to solve the issue. If it helps, then well for you. However, if this method doesn’t work for you, then go ahead and try the next one.

2. Analyze the Network Connection Settings

One more reason why the phone transmits an MMI error to you is because of the lack of network connection. In case the MMI code you have sent is the code to inspect the prepaid balance, or particularly a function of the network operator, ensure that the device is linked to your network.

In case you are not receiving any signal, then the device is not linked to your network yet. So, now you will have to reconnect it manually. Usually, it connects on its own, but sometimes you will have to manually choose your service provider to connect to their specific network.

To Do This Process, Follow the Steps.

  • 1. Head to Settings.
  • 2. Select the Wireless and Networks option.
  • 3. Then, click on the More Networks option (In case you use two different SIM, pick the SIM that you want to view).
  • 4. Choose Mobile Network.
  • 5. Now, pick Manual Selection (The device will begin looking for the available networks).
  • 6. Select the desired network that you want. Wait for some time to allow the device to connect; otherwise, you will have to redo the process until the device is connected. Until you see the signal bars, there are no chances to solve the connection problem or invalid MMI code error.

Usually, this is the procedure for all Android phones with UI and stock Android ROM. If you see the signal displaying LTE, 3G, 4G, and others, then you should understand that the device is connected to a network. Try to dial the MMI code once again.

Hopefully, this solution is going to help you solve the issue. However, don’t get disheartened if it doesn’t help. We have other solutions too. So, you can try the rest of them and see if the issue gets resolved.

3. Turn off or use 1 SIM

In case you use 2 SIM, and the calls, data, or texts automatically route to a specific network without asking you to pick a network manually; then there is a chance that the phone is transmitting the MMI code to the wrong network.

To Isolate the Error, You Have Three Options.

  • 1. Put the device to prompt for the manual selection of the network.
  • 2. Put one SIM out of action.
  • 3. Get rid of the other card physically.

Set the device for manual selection of the mobile network to the ‘Always ask’ option before placing a call. To enable this option, follow these steps.

  • 1. Head to the Settings application.
  • 2. Look for Dual SIM Settings/SIM Settings.
  • 3. Then, choose Call/Voice.
  • 4. Tap on the ‘Always Ask’ option.

In case you want to stop the usage of the other SIM, remove the name of the network of the SIM you want to disable by following the same steps as before. The last option is inconvenient, but it is the most effective solution to get rid of this issue. The procedure of removing the card manually makes the device pick the network of the remaining SIM.

4. Restart the Device

Restarting the device will refresh every single operation. There are times when the errors on the device are a result of some basic system issues. This can be easily solved via a restart process. Therefore, it is advisable to restart the device if the other techniques have already been used.

Restarting the device will surely fix the connection problem or the invalid MMI code issue.

5. Move to the Safe Mode

Certain cases show that the MMI code is due to specific software or any application which is installed on the device. Most users repair the connection problem or invalid MMI code issue by deleting a few applications on the device that stop the code from reaching the network operator.

If you reboot the device into Safe Mode, the device will not be able to load the third-party applications. Just the stock application will be available, which came along with the original Operating System (OS).

Moreover, it means that every application that you have installed won’t be available in Safe Mode. This will assist you in determining whether the applications you have installed are leading to a connection problem or an invalid MMI code error.

Moving to Safe Mode is the last option. If all the techniques have failed to solve the connection problem or invalid MMI code error, then use this method. It is quite easy to execute the whole procedure, and your device will get back to its original state as soon as you reboot it.

Follow the Steps Written Below to Move the Device to the Safe Mode.

  • 1. Press and hold the off (power) button for some seconds until the device shows a box to confirm that you wish to reboot the device again.
  • 2. Click on the ‘OK’ option, and the device will no more restart to Safe Mode.

As soon as your device gets into Safe Mode, try to enter the MMI code once again. Do this to see if the connection problem or invalid MMI code error still persists. In case you witness the error, it means that one application that you have installed on the device is resulting in the error.


Q1: What is an MMI code? An MMI code, or Man-Machine Interface code, is a series of characters that allow users to access specific functions or features on their mobile devices directly.

Q2: Why am I getting the ‘Connection Problem or Invalid MMI Code’ error? This error can occur due to various reasons, including inadequate network signal strength, incorrect dialing formats, software or firmware issues, or problems with the SIM card.

Q3: How can I fix the error if I have a weak network signal? If you have a weak network signal, try moving to an area with better reception or waiting until the signal strength improves. You can also try restarting your device or contacting your network provider for assistance.

Q4: What should I do if the troubleshooting steps don’t work? If the troubleshooting steps mentioned in this article don’t resolve the error, it is recommended to contact your network provider’s customer support for further assistance and guidance.

Q5: Can I prevent the error from occurring in the future? Yes, you can prevent the ‘Connection Problem or Invalid MMI Code’ error from occurring in the future by keeping your device’s software updated, using correct dialing formats, and ensuring proper SIM card insertion.

Also, learn more about how to fix your iPad won’t connect to Wi-Fi issues with ease.


With this, we end this section where we tried to cover every possible solution to the connection problem or invalid MMI code error. We believe that these methods will surely assist you in resolving the issue. All the methods are reliable and quite easy to follow. You don’t require any technical help to use these solutions.

The connection problem or invalid MMI code error is pretty easy to repair. However, in case you feel that you need help, feel free to contact us. We offer 24/7 support. So, we will guide you anytime you need us. Also, if you try any solution that is written in the article, do not forget to share your review and experience.

And if you have any other solution except the ones in the article, enlighten us. We will be glad to know. Thank you for taking out the time to read our article. We hope that this was helpful to you in solving the connection problem or invalid MMI code error.


Skilled software testing specialist with expertise in comparisons and research, passionate about blogging, reviews, and creating video tutorials.