Why Xiaomi’s second SIM doesn’t work: The Complete Guide

A situation when one of the flagship or budget devices ceases to function SIM-This is especially frustrating when it comes to the Xiaomi brand, which is famous for its functionality and support for two active numbers, and can be a simple software failure, as well as more serious hardware damage.

Before you bring your device to the service center, you need to do a series of self-checks, often the solution lies in the wrong settings of the network or physical contamination of contacts. In this article, we will discuss in detail all possible scenarios why the second SIM on your phone does not work, and provide step-by-step instructions for restoring communication.

Now, the smart phones today have a complex architecture of radio modules, and IMEI failures or antenna plume damage can cause a complete lack of signal on one of the slots, and our goal is to find the root of the problem by eliminating it.

Physical examination SIM-card-slot

The first and most obvious step is to eliminate physical defects. Often users forget that the second SIM may have oxidized or shifted in the tray. Remove the tray with a paper clip and carefully examine the contacts on the map itself and inside the phone.

Note which slot stopped working.In some Redmi and Poco models, the first slot is a priority and supports a wider range of frequencies, while the second can be limited to the standard. 2G/3G In certain modes of operation, if you use the old SIM-hand-carved cards may not fit tightly into the contacts.

If you change the cards, if the problem moves with the card, it's the card itself, and you have to replace it with the operator, and if the second slot is silent regardless of the card you insert, the problem goes deeper.

It's also worth checking if the tray itself is deformed. Microscopic bending can prevent the chip from connecting normally to the motherboard. Insert the tray before the characteristic click, but without undue effort.

Network settings and operator selection

If the map is physically OK, we'll move on to the software part. MIUI and the new HyperOS mobile network settings may be disrupted after an update or manual intervention. → SIM-maps and mobile networks.

Make sure the second SIM card has a Use Switch activated. Sometimes, after a system update, the system automatically turns off the secondary slot to save energy or avoid conflicts. Also check the network type settings: if there is a mandatory restriction on only 5G, and in your area only 4G catches, the phone will not be able to register with the network.

⚠️ Attention: Establishment of the “Only” regime 4G» or "Only" 5G» through the engineering menu can cause complete signal loss if the operator does not support voice calls via VoLTE in your area.

The important parameter is the choice of the operator. SIM-If you find the map, find Network Selection, and switch it from Automatic to Manual Search, if the phone finds the networks available and asks you to sign up, it means that the module is good.

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If automatic network search is not working, try to manually select a non-operator (for example, MTS instead of Beeline). If the phone tries to register and gives an authorization error, this is a good sign, then the radio module works.

Remember, VoLTE. If your carrier supports this technology, it should be enabled in the settings. If you don't support VoLTE on one of the sims, you can drop calls or you can't use the Internet and voice at the same time.

Failure of firmware and reset network settings

Software errors are a common reason why the second SIM on the shaomi phone doesn't work. Accumulated cache files or conflicts after an Android update can disrupt the modem. The safest way to fix this is to reset your network settings.

This procedure won’t delete your personal photos or contacts, but will return all network settings to factory values.You’ll have to re-enter Wi-Fi passwords and configure Bluetooth devices, but this often reanimates a dead slot.

To perform the reset, go to Settings → Connection and Sharing → Reset Wi-Fi, mobile networks and Bluetooth. Confirm the action and wait for the device to restart.

If the reset didn't work, it might be a specific version of the firmware that's a problem. Forum users often report bugs in certain MIUI builds where the second SIM's IMEI disappears, so waiting for an update or rolling back to a stable version will help.

Problems with IMEI and radio module

One of the most serious problems is loss. IMEI. This is a unique device identifier, without which the phone cannot work on the cellular network. SIM-maps instead of numbers are displayed dashboards or zeros, so there was a failure in the section NVRAM.

You can check for IMEI by dialing *#06# in the dialer code. If the second slot does not display the number, the software methods may be powerless, often after a failed flashing of the phone or interference with system files.

Recovery IMEI — complex procedure requiring root rights and special software (e.g. Xiaomi) ADB/Fastboot Tools or engineering utilities. It is better for the average user not to take up this on their own, since there is a risk of finally "blocking" the communication module.

⚠️ Attention: Change or forgery IMEI Restore only the original number if it was lost due to a software failure.

If the IMEI is in place but there is no connection, the radio frequency module itself may have failed, and this is the chip that handles the reception and transmission of the signal, and it can only be replaced in a service center with soldering equipment.

Conflict of Android Versions and Regional Settings

Global versions of Xiaomi firmware sometimes have limitations related to regional communication standards, for example, a Chinese version of the phone, flashed to a global one, may not work correctly with the frequencies used by local operators for the second SIM.

Also, some features, such as Dual 4G or Dual VoLTE, may be software-limited in certain regions. Check the device region in the Settings menu → Additional Settings → Region. Changing the region to China or India will sometimes unlock the modem's hidden capabilities.

It’s also worth mentioning the conflict with call management apps, which means that if you install a third-party dialer or call recording app, it can take control of the second SIM, causing it to malfunction.

It is important to understand the difference between the global (Global) and Chinese (CN) versions. The Chinese versions often lack some bandwidth (Band 20), which is critical for 4G operation in rural Europe and Russia, which can be perceived as a malfunction of the second SIM.

Hardware damage and problem solving

If all software methods are exhausted and the second SIM doesn't work, it's probably just the hardware, falling, getting moisture, or just factory defects, which can lead to the antenna contacts being detached or the plume being damaged.

In modern Xiaomi smartphones, antenna terminals are often located on the bottom and top edges. Even a slight impact can disrupt contact. Diagnostics in the service will show whether there is a signal at the exit of the module, and where exactly the cliff occurs.

In some cases, simply re-ploughing a modem chip or replacing an antenna module helps, and if the phone is warranty-free, don't try to open it yourself, which will result in a denial of warranty service.

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If resetting network settings and reshuffling cards did not help, and IMEI is saved - there is a high probability of hardware malfunction of the antenna path or the modem itself.

Don’t ignore the problem if the phone starts to warm up strongly in the camera area or upper body when trying to find the network.This may indicate a short circuit in the power supply of the radio module.

Frequently Asked Questions (FAQ)