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How to Fix iPhone 4G Network Issues in Japan

  • The article explains the possible causes and solutions for iPhone 4G network issues in Japan, such as updating carrier settings, resetting network settings, checking frequency bands, and troubleshooting hardware or software issues.
  • The article also provides some FAQs and tips to help users optimize their iPhone’s network performance in Japan, such as turning on Wi-Fi Assist, using a VPN, and contacting their carrier.

Japan is one of the most advanced countries in terms of mobile technology, offering fast and reliable 4G and 5G networks to its users. However, some iPhone users may encounter issues with their 4G network connectivity, such as frequent disconnections, slow speeds, or no service. This can be frustrating and inconvenient, especially if you rely on your iPhone for work, travel, or entertainment.

In this article, we will explain why this problem occurs and how to fix it using simple steps. We will also provide some FAQs and tips to help you optimize your iPhone’s network performance in Japan.

How to Fix iPhone 4G Network Issues in Japan

Why Does My iPhone Disconnect from 4G Network in Japan?

There are several possible reasons why your iPhone may disconnect from the 4G network in Japan, such as:

  • Incompatible carrier settings: Carrier settings are files that contain information about your carrier’s network and related features, such as voice and data services, Wi-Fi calling, and 5G. If your carrier settings are outdated or incompatible with the Japanese network, your iPhone may not be able to connect properly to the 4G network or use some of its features.
  • Incorrect network settings: Network settings are preferences that control how your iPhone connects to cellular and Wi-Fi networks. If your network settings are incorrect or corrupted, your iPhone may have trouble finding or staying connected to the 4G network.
  • Unsupported frequency bands: Frequency bands are ranges of radio frequencies that are used by cellular networks to transmit data. Different countries and carriers use different frequency bands for their 4G networks. If your iPhone does not support the frequency bands used by the Japanese carriers, you may experience poor or no 4G network coverage.
  • Hardware or software issues: Sometimes, the problem may be caused by a faulty SIM card, antenna, or other hardware components of your iPhone. Alternatively, it may be due to a software glitch, bug, or malware that interferes with your iPhone’s network functionality.

How to Fix iPhone 4G Network Issues in Japan

Depending on the cause of the problem, there are different ways to fix your iPhone’s 4G network issues in Japan. Here are some of the most common and effective solutions:

Solution 1: Update Your Carrier Settings

One of the first things you should do is to check if there is a carrier settings update available for your iPhone. A carrier settings update can improve your iPhone’s compatibility and performance with the Japanese network and enable new features such as 5G or Wi-Fi calling. To update your carrier settings manually, follow these steps:

  1. Make sure that your device is connected to Wi-Fi or a cellular network.
  2. Tap Settings > General > About.
  3. If an update is available, you’ll see an option to update your carrier settings. Tap Update and follow the onscreen instructions to install the update.

If you set up a new eSIM or insert a new SIM card into your iPhone, you might need to download the carrier settings for your new carrier. To see the version of carrier settings on your device, tap Settings > General > About and look next to Carrier.

Solution 2: Reset Your Network Settings

Another way to fix your iPhone’s 4G network issues in Japan is to reset your network settings. This will erase all your saved Wi-Fi passwords, VPN configurations, Bluetooth connections, and cellular preferences, and restore them to their default values. This can help resolve any network-related errors or conflicts that may be causing the problem. To reset your network settings, follow these steps:

  1. Open Settings and tap General > Transfer Or Reset iPhone.
  2. Tap Reset > Reset Network Settings.
  3. Enter your iPhone’s passcode, then tap Reset Network Settings once again to confirm your decision.

Your iPhone will turn off, complete the reset, then turn itself back on again.

Solution 3: Check Your Frequency Bands

If you are using an overseas iPhone in Japan, you may need to check if it supports the frequency bands used by the Japanese carriers for their 4G networks. According to Kimovil, these are the frequency bands supported in Japan:

  • KDDI au: B1 (2100), B3 (1800), B11 (1500), B18 (800), B26 (850), B28a (700), B41 (TDD 2500), B42 (TDD 3500)
  • NTT Docomo: B1 (2100), B3 (1800), B19 (800), B21 (1500), B28b (700), B42 (TDD 3500)
  • Softbank: B1 (2100), B3 (1800), B8 (900), B11 (1500), B28b (700), B41 (TDD 2500), B42 (TDD 3500)
  • Rakuten Movile: B3 (1800), B18 (800)

To see the frequency bands supported by your iPhone model, you can visit the Apple website and select your device. Alternatively, you can use a third-party app such as Network Cell Info Lite to check the frequency band of your current network connection.

If your iPhone does not support the frequency bands used by the Japanese carriers, you may experience poor or no 4G network coverage. In that case, you may need to switch to a different carrier, use a local SIM card, or upgrade to a newer iPhone model that supports more frequency bands.

Solution 4: Troubleshoot Hardware or Software Issues

If none of the above solutions work, you may need to troubleshoot your iPhone’s hardware or software issues that may be affecting your 4G network connectivity. Some of the steps you can take are:

  • Restart your iPhone: Sometimes, a simple restart can fix many network-related problems. To restart your iPhone, press and hold the power button until you see the slide to power off option. Swipe the slider to turn off your iPhone, then press and hold the power button again to turn it back on.
  • Remove and reinsert your SIM card: Your SIM card may be loose, damaged, or dirty, which can cause network issues. To remove and reinsert your SIM card, use a SIM eject tool or a paper clip to open the SIM tray on the side of your iPhone. Take out the SIM card and wipe it gently with a soft cloth. Then, put it back into the SIM tray and push it back into your iPhone.
  • Update your iOS: Updating your iOS can fix any software bugs or glitches that may be interfering with your 4G network performance. To update your iOS, go to Settings > General > Software Update. If an update is available, tap Download and Install and follow the onscreen instructions to complete the update.
  • Restore your iPhone: Restoring your iPhone can erase all your data and settings and reinstall the latest version of iOS. This can help resolve any deep-rooted software issues that may be causing the problem. However, before you restore your iPhone, make sure you have a backup of your data either on iCloud or iTunes. To restore your iPhone, follow these steps:
    1. Connect your iPhone to a computer with iTunes installed.
    2. Open iTunes and select your device from the top left corner.
    3. Click Restore iPhone and confirm your choice.
    4. Wait for iTunes to download and install the latest iOS on your iPhone.
  • Contact Apple Support or your carrier: If none of the above steps work, you may have a hardware issue that requires professional repair or replacement. You can contact Apple Support or your carrier for further assistance.

Frequently Asked Questions (FAQs)

Question: How do I know if my iPhone is connected to 4G in Japan?

Answer: You can check if your iPhone is connected to 4G in Japan by looking at the status bar at the top of your screen. If you see a 4G icon next to the signal strength indicator, it means you are connected to a 4G network. If you see an LTE icon, it means you are connected to a faster version of 4G called LTE (Long Term Evolution). If you see a 5G icon, it means you are connected to a 5G network, which is even faster than LTE.

Question: How do I enable or disable 4G on my iPhone in Japan?

Answer: You can enable or disable 4G on your iPhone in Japan by going to Settings > Cellular > Cellular Data Options > Voice & Data. Here, you can choose between different options depending on your iPhone model, carrier, and region:

  • LTE: This option enables both voice and data over LTE when available.
  • LTE (Data Only): This option enables only data over LTE when available. Voice calls will use older networks such as 3G or 2G.
  • 3G: This option disables LTE and uses only 3G networks for voice and data.
  • 2G: This option disables LTE and 3G and uses only 2G networks for voice and data.

Enabling or disabling 4G can affect your data speed, battery life, and network coverage. Generally, using higher-speed networks such as LTE or 5G can improve your data performance but drain your battery faster. Using lower-speed networks such as 3G or 2G can save battery life but reduce data speed and quality.

Question: How do I switch between different carriers in Japan?

Answer: If you have an unlocked iPhone that supports multiple carriers in Japan, you can switch between them by going to Settings > Cellular > Network Selection. Here, you can turn off Automatic and manually select a carrier from the list of available networks. You may need to wait for a few seconds for your iPhone to register with the new carrier.

Alternatively, if you have an eSIM card or a dual SIM iPhone, you can switch between different eSIMs or SIM cards by going to Settings > Cellular > Cellular Plans. Here, you can select a different eSIM or SIM card for your cellular data, voice calls, and messages.

Question: How do I optimize my iPhone’s network performance in Japan?

Answer: There are some tips and tricks you can use to optimize your iPhone’s network performance in Japan, such as:

  • Turn on Airplane Mode and then turn it off: This can help refresh your network connection and resolve any temporary issues.
  • Turn on Wi-Fi Assist: This feature automatically switches to Wi-Fi when your cellular data connection is poor. To turn on Wi-Fi Assist, go to Settings > Cellular > Wi-Fi Assist and toggle it on.
  • Turn off Background App Refresh: This feature allows apps to update their content in the background when you are not using them. However, this can consume your cellular data and battery life. To turn off Background App Refresh, go to Settings > General > Background App Refresh and toggle it off.
  • Use a VPN: A VPN (Virtual Private Network) can help you bypass any network restrictions or censorship that may affect your 4G network access or speed. However, be aware that some VPNs may slow down your connection or compromise your privacy. To use a VPN, you need to download a VPN app from the App Store and follow its instructions to set it up.
  • Contact your carrier: If you have any questions or issues with your 4G network plan, coverage, or features, you can contact your carrier for support. You can find their contact information on their website or app.


In this article, we have explained why some iPhone users may experience 4G network issues in Japan and how to fix them using simple steps. We have also provided some FAQs and tips to help you optimize your iPhone’s network performance in Japan. We hope this article has been helpful and informative for you. If you have any feedback or suggestions, please let us know in the comments section below.

Disclaimer: The information in this article is based on our research and experience and is not intended to be a substitute for professional advice. We are not affiliated with Apple, any of the carriers mentioned, or any of the apps or websites referenced. We do not guarantee the accuracy, completeness, or timeliness of the information in this article. Please use this information at your own risk and discretion.

Alex Lim is a certified IT Technical Support Architect with over 15 years of experience in designing, implementing, and troubleshooting complex IT systems and networks. He has worked for leading IT companies, such as Microsoft, IBM, and Cisco, providing technical support and solutions to clients across various industries and sectors. Alex has a bachelor’s degree in computer science from the National University of Singapore and a master’s degree in information security from the Massachusetts Institute of Technology. He is also the author of several best-selling books on IT technical support, such as The IT Technical Support Handbook and Troubleshooting IT Systems and Networks. Alex lives in Bandar, Johore, Malaysia with his wife and two chilrdren. You can reach him at [email protected] or follow him on Website | Twitter | Facebook

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