My phone keeps showing ‘Connection Problem or Invalid MMI Code.’ It happens when I try to dial certain codes. Does anyone know how to fix this?

This is a common issue on Android devices. Here’s how you can fix it.

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What is an MMI Code?

An MMI (Man-Machine Interface) code is also called a USSD code. It’s a sequence of numbers and symbols you can dial to access carrier functions. These codes usually start or end with * or #.

How To Fix Connection Problem or Invalid MMI Code

1. Third-Party App

Sometimes a third-party app causes the invalid MMI code error. The easiest way to check is by entering Safe Mode. In Safe Mode, your phone won’t run any third-party apps.

How to Enter Safe Mode

• Turn your phone off by pressing and holding Power, then Power Off.
• Press and hold Power + Volume Down together to turn it back on.
• Release the Power button once the screen lights up, but keep holding Volume Down.
• You’ll see “Safe Mode” at the bottom-left of the screen.

How to Exit Safe Mode (3 Ways)

1. Press and hold Power for at least six seconds, then tap Restart.
2. Press and hold Power + Volume Down for about five seconds.
3. Swipe down from the top of the screen, tap Safe Mode is on, then restart.

Now dial the prefix code (like *135#) in Safe Mode. If it works, remove any recently installed apps that might be causing the conflict.

2. Prefix Code

A quick fix is adding a comma (,) or a plus sign (+) in your MMI code.

• Example: If your code is *2904*7#, try *2904*7#, or *+2904*7#.

3. The Information Mode

Use your phone’s device information mode to turn on IMS over SMS.

• Open the dialer and enter *#*#4636#*#*.
• Select Device/Phone Information.
• Tap Run Ping Test.
• Tap Turn Off Radio.
• Tap Turn on SMS over IMS.

4. Reset Network Settings

Resetting your network settings might solve MMI errors.

• Go to Settings.
• Tap General Management (or System, depending on your device).
• Select Reset.
• Tap Reset network settings.

5. Reset All Settings

If network resetting isn’t enough, reset all settings.

• Go to Settings.
• Tap General Management.
• Select Reset.
• Tap Reset settings.

6. Network Operator

Manually choose your network operator.

• Go to Settings > Connections (or Wireless & Networks).
• Tap Mobile Networks.
• Tap Network Mode.
• Choose Search Now.
• Select your network.

7. Set Network Mode to Auto

Let your phone switch between 4G, 3G, or 2G automatically.

• Open Connections or Wireless & Networks.
• Tap Mobile Networks.
• Tap Network Mode.
• Choose 4G/3G/2G (auto connect).

8. Update APN Settings

Make sure your APN settings are correct.

• Go to Settings > Connections > Mobile Networks > Access Point Names.
• Tap the menu (three dots), then Reset to Default.
• Enter updated APN info if needed.

9. Activate SIM Card

Make sure your SIM is active.

• Go to Settings > Connections.
• Tap SIM card manager.
• Enable your SIM card.

10. Perform a Software Update

Updating your phone can fix bugs that cause MMI errors.

• Go to Settings.
• Scroll down and tap Software Update.
• Install any available updates, then reboot.

11. Call Your Carrier

If none of these steps help, contact your carrier. They can check for network outages or replace your SIM if needed. Also make sure you have an active data plan.

If you have more questions or need further help, let us know.

FAQs

Why do I get “Invalid MMI Code” on my phone?

It usually happens if you type the code incorrectly or your carrier restricts the code. Network glitches and SIM card issues can also trigger it.

How do I fix the MMI error without resetting my phone?

Start by adding a comma or plus sign to the end of the code, then try safe mode. If that fails, you can reset network settings.

Will safe mode delete my data or apps?

No. Safe mode only disables third-party apps temporarily. Your data stays intact, and all apps return once you exit safe mode.

How do I know if my SIM is causing the error?

Try inserting your SIM in another phone or contact your carrier. A damaged or inactive SIM might cause MMI code errors.

Can an outdated phone software cause MMI code problems?

Yes. An outdated OS may have bugs. Updating your software can often fix the issue.