Modern Xiaomi smartphones are almost always equipped with a hybrid or full-fledged dual slot, which allows users to stay in touch on two different networks at the same time. However, when you first buy a device or after replacing a SIM card, many owners face a situation where the second card is not determined or the system does not offer to choose the mode of operation.
Most often, the problem is not hardware failure, but software settings or module installation, and in the MIUI operating system and the new HyperOS, slot management is placed in a separate menu where you can flexibly adjust the priorities of the Internet and voice calls.
In this article, we will take a look at all the steps of activation, from the physical installation to fine-tuning network settings, and you will learn why the phone may not see the second SIM and how to force the slot to run through system settings.
Physical installation and tray inspection
The first step before any software manipulation should be to check the physical setup. The SIM card tray on Xiaomi smartphones is usually located on the lower or upper end of the case and is removed using a special clip.
This means that the second compartment can be designed for either a second SIM card or a MicroSD card, but not both.If you insert the memory card, the second SIM slot is automatically locked programmatically and physically.
- 📱 Make sure that the SIM card is trimmed according to the Nano-SIM standard and does not have chips on the contacts.
- 🔍 Check the orientation of the chip: the golden contacts should look down, and the beveled angle coincides with the pattern on the tray.
- 🔌 Carefully insert the tray before clicking, without putting excessive effort to avoid damaging internal contacts.
Once the device is turned on, the system should automatically detect a new card. If this does not happen, try to wipe the SIM card contacts with a soft dry cloth. Sometimes oxidation or dust prevents normal connection to the phone's reader module.
⚠️ Warning: Never try to insert the tray backwards or forcefully, this can cause the reader to break down, the repair of which will require disassembling the body.
☑️ Installation verification SIM
Basic activation in the settings menu
If the card is physically set correctly, but the second slot is still not active, you need to refer to the software interface. In the MIUI shell, the card management settings are located in the section responsible for wireless networks. The path may vary slightly depending on the firmware version, but the logic remains the same.
You need to go to the Settings menu, then select the item SIM-And that's where you see the status of both slots, and if the second slot is off, you'll see a switch next to the operator's name or the label "SIM 2" which must be activated.
Once the switch is turned on, the system will ask you to confirm the action or select your preferred default settings, which is a critical step, since without assigning tasks, the slot can remain in passive standby mode.
Set up priorities and network modes
After the successful activation of both slots, the user faces the question of resource allocation. The smartphone cannot simultaneously transmit data through two SIM cards at maximum speed, so you need to choose which one will be responsible for mobile Internet and which will be responsible for voice communication.
On the menu. SIM-You can find the default section for maps and mobile networks, and you can assign the main card for calls and a separate card for data transfer, and you can also look at the "Preferred type of network" item".
For modern use, it is recommended to choose LTE or 5G mode, if your model and operator support these standards. However, in areas of uncertain reception, switching to 3G or 2G for one of the cards sometimes helps to unload the radio module.
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Table of comparison of slot modes
Understanding the difference between modes helps avoid confusion when setting up. Below is a table showing how slots behave in different configurations.
| Parameter | One active slot | Two active slots (4G/4G) | Energy saving regime |
|---|---|---|---|
| Battery consumption | Low. | High. | Minimum |
| Internet speed | Maximum | Only one map. | Limited. |
| Second line availability | Unavailable | Standby mode | Standby mode |
| Heating the hull | Minimum | Possible under load | Absent. |
Using two active SIM cards in a constant network search mode (for example, on a trip) can significantly reduce battery life. If you do not need both numbers right now, it is wiser to temporarily disable the second slot programmatically.
Solving the Problems of Defining the Second Card
It's not uncommon for the first slot to work perfectly and the second slot to fail, often because of a conflict of program profiles or network cache, and the first thing you can do is try to do a simple reboot of the device, which often resolves temporary modem failures.
If the reboot didn’t help, check if the second SIM card is locked. PIN-It's also worth making sure that the SIM card itself is active and not blocked by the carrier.
- 🔄 Switch the SIM cards: insert the problem card into the first slot. If it works there, then the problem may be in a particular slot or its contacts.
- 📡 Reset your network settings: go to Settings → Connection and sharing → Reset Wi-Fi, mobile networks and Bluetooth.
- 🛠 Check for system updates: Sometimes SIM card detection bugs are patched in new security patches.
⚠️ Note: When you reset your network settings, all saved passwords from Wi-Fi and Bluetooth pairs will be deleted. Make sure you remember the data for your home Internet connection.
💡
If the second SIM card is old and hand-cut with scissors, it may not work properly in today's narrow trays. Contact the communications salon for a free replacement with a new nano format.
Specificity of work in different regions
Xiaomi smartphones often have regional firmware versions (Global, China, Europe, Russia). Some Chinese versions (CN) may not support certain LTE frequencies used in Europe or the CIS, which affects the performance of the second SIM card.
In addition, in some models, when using two SIM cards, the maximum Internet speed is limited, since the radio module divides the resource between two subscribers, which is normal behavior for most modern Qualcomm and MediaTek chipsets.
If you are using a phone brought from another region, make sure that the settings are the right region. Go to Settings → Additional settings → Region and your country selection can open access to the required frequencies and operator settings.
💡
Choosing the right region in your phone settings can solve network definition and 4G problems on the second SIM card.