There are many common problems that we are getting while executing USSD requests. Sometimes these are related to carriers and sometimes it is device-specific.
Very common problem is Connection problem or Invalid MMI code
What is MMI code?
Man-Machine Interface code or MMI code are characters that begin with a star (*) or hash (#). It is used to obtain a variety of information or enable special commands on your smartphone. For instance, entering *#06# on Global System for Mobile communication (GSM) phones will display the model and the serial number of the phone.
There are several reasons why the “Connection problem or invalid MMI code” error message appears on your phone. The main reason is an issue with the carrier provider or problems with the SIM authentication on the smartphone. The error is quite common for phones with dual-SIM capabilities, but it does occur on others too.
There are plenty of ways to resolve this problem, such as:
Restart the Android Device
The first way to try to fix an invalid MMI code would be to restart the smartphone.
- Hold the Power button and the Home button at the same time until the phone turns off and starts vibrating; wait for it to restart.
- Alternatively, press and hold the Power Button until the Shutdown options menu appears, and then select Restart.
Run Your Device in Safe Mode
It’s possible that third-party software is interfering with your connection and causing an MMI error. Fortunately, it’s easy to rule this out. Here’s what to do:
- Restart your phone in Safe Mode. You can do this by holding the power button (button combination) on your Android device. Then, long-press the Power icon.
- Tap Safe Mode from the menu that appears.
- Now, use your phone in Safe Mode for a bit to see if the MMI error appears.
If your phone still doesn’t throw any error codes, third-party software is interfering with your network. You’ll need to start removing third-party apps. Start with the applications you installed around the time you started seeing the error.
When you follow the Settings>Apps path scroll down and uninstall any apps you believe may be the culprit. Then, power your phone out of Safe Mode and see if the error appears. Keep doing this until the MMI code ceases.
Use Airplane Mode
Some users have had success using Airplane Mode to resolve their MMI code error issues.
Go to Settings and turn Airplane Mode to On.
Wait about 10-30 seconds, and then turn Airplane Mode to Off.
Given that an MMI Code error can occur due to weak signal strength performing this can reset your connection and correct the error.
Reset Your Network Settings
Because we know that the MMI error indicates an issue with your device’s cellular connection, the next logical step is to reset your Network Settings. Perhaps your network settings haven’t updated properly or there’s a glitch in the system. Performing a network reset will clear any problem codes and help you start fresh. Here’s what to do:
Open Settings on your Android device. Then, tap on General Management.
You can also use the search icon and type ‘Reset’ to skip step 2.
Scroll down and tap on Reset.
Tap Reset Network Settings.
Tap Reset settings to confirm. Your phone will restart.
When your phone powers back up, the error should disappear.
Modify the Prefix Code
Another way to fix the Connection Problem or Invalid MMI Code on an Android smartphone would be to add a comma at the end of the Prefix code. When a comma gets added, it forces the operation to execute and overlook any error.
Below are two different ways to modify the prefix code.
- If the Prefix code is (*2904*7#), then add a comma at the end, similar to this (*2904*7#,).
- You can use the + symbol after * similar to this (*+2904*7#).
Activate Radio
Now, this is another trick to fix the issue. So, see to it that you enter the information regarding your device and activate the radio to turn on IMS over SMS.
Below are a couple of steps that you need to follow to do so:
- Dial *#*#4636#*#* \
- Navigate the device information
- Select ‘Run Ping Test’
- After the test is complete, choose the option to turn off the radio
- Then, press ‘Turn on SMS over IMS’
- Lastly, reboot your phone device
Turn Off One SIM Card
As we know, dual SIM cards are prone to MMI code errors. So, the first thing that you need to do here is to turn off the unused SIM card to solve the problem.
To switch off the SIM card, follow these steps:
- Go to ‘SIM Card Manager’ on your device
- Turn off the unused card
- Test to see if it works
In case you’re unsure about which sim is currently in operation, test both of them and check if the trick works.
Clear Mobile Data and Cache
The MMI code error can also occur if specific data is corrupting the device. So, the only thing left to do here is to clear the mobile data and cache that is causing an error.
In order to do so, let’s take a look at these steps given below:
- Go to ‘Settings’
- Choose ‘Applications’
- Select ‘Contacts’ and press ‘Mobile Data’
- Choose the options to clear the data
Once you clear the data with the above-mentioned steps, check to see if it works.
If this problem still does not resolve for you then you need to talk to your network's customer support team.