Update AT&T HTC One A9 (1.27.502.5) 6.0 Marshmallow


New Firmware/ ROM Update available for AT&T HTC One A9, and you can manually download and install it if you can't get it through the OTA method.

If you are going to upgrade your AT&T HTC One A9 firmware to the latest update (1.27.502.5) Android 6.0 Marshmallow, then you should know there are several ways to do that, but in this guide I will explain only two official methods. The two methods that I mentioned is the OTA method and the other method is the manual method if you can't get this update through the OTA. The manual method that I mentioned is an official method also like OTA, and to upgrade the AT&T HTC One A9 firmware to 1.27.502.5 Android 6.0 Marshmallow manually you will do it through HTC Sync Manager.

Update AT&T HTC One A9 (1.27.502.5) 6.0 Marshmallow

AT&T HTC One A9 Update methods Summary:

1- OTA (Over The Air) method:
- In this method you will download and install the update through your AT&T HTC One A9 device.

2- The Manual method:
- In this method you will use HTC Sync Manager on your PC.

It's recommended to upgrade your current firmware to the latest version, so that you will get the new improvements or the enhancements to your AT&T HTC One A9. Firmware Upgrade isn't that the hard process that you will not be able to do, it's just some steps you can do to complete the upgrade process successfully, so if you will do it for the first time, then you need to focus and be careful and after that you be a master.

WARNING: This Firmware Update was released only for AT&T HTC One A9, and not for any other model, so Yes Android USA is not responsible for any damage caused in your phone. Do it at your own risk, and please don't mistake and do it the right way.



AT&T HTC One A9 (1.27.502.5) Android 6.0 Marshmallow System Update Changelog


This software upgrade available for your AT&T HTC One A9 provides the following key enhancements:
  • Battery life improvements.
  • Camera improvements.
  • System enhancements.
  • Android Security Patch update.

Before you proceed, please confirm that this software upgrade to 1.27.502.5 is a newer version than what is currently loaded on your device. If it is the same version, there is no need to reload the software. Navigate to the Home screen, then tap All apps > Settings > About and locate the Software information . If your Software number is less than 1.27.502.5 , you should proceed with the upgrade.

WARNING: During the upgrade process the device will reboot multiple times and show software upgrade screens. Do not remove the AC charger or long-press the Power button as this might stop the update and your device may be rendered inoperable!

Important points to be noted before upgrading the AT&T HTC One A9 Firmware to (1.27.502.5) Android 6.0 Marshmallow


Before you proceed with the update, make sure you have done the following:
  • Set aside approximately 20 minutes to allow the device to update.
  • Connect the device to a charger.
  • Ensure the battery is charged to at least 35% .
  • Ensure the device is connected to AT&T 4G/LTE and a stable Wi-Fi network.

Related To HTC One A9


Methods to install the (1.27.502.5) Android 6.0 Marshmallow on AT&T HTC One A9

OTA Method:

To download and install the update from the device through OTA, follow these steps below:
  • Follow the "Important Points" steps that I mentioned above.
  • From the Home screen tap All apps , tap Settings .
  • Tap AT&T software update .
  • Tap Check for updates .
  • Tap Continue to download the update.
  • If downloading the update using the mobile data network (not connected to Wi-Fi), you may be prompted with a data fee warning message. If this is acceptable, tap YES to start the upgrade process.
  • The status of the download can be checked in the Notifications pull down.
  • Once the download is complete, the user will be prompted to install from the Notifications pull down. Tap the System update to begin the upgrade process.
  • Tap OK to begin the update process to software version 1.27.502.5 .

WARNING: During the upgrade process the device will reboot multiple times and show software upgrade screens. Do not remove the AC charger or long-press the Power button as this might stop the update process and your device may be rendered inoperable!

  • The device will reboot and begin installation. Users will not be able to use their device during the installation process (approximately 10 minutes).
  • Once the system update is complete, tap OK to continue.
  • For best performance, open Play Store and tap the Menu icon, then select My apps and ensure all installed apps are updated.
Watch this video from AT&T which explain the System Update through OTA:




Manual Method:

Manual system update instructions using HTC Sync Manager:

If you are outside of AT&T/Wi-Fi coverage, or the update is not found, you may perform a manual system update via USB connection to a PC. This process requires that you download and install HTC Sync Manager first in order to get the proper drivers. If you do not have HTC Sync Manager installed already, you may download it from Here.

WARNING: Performing the system update manually will delete all information from the device. Ensure all information is backed up before proceedin.

Performing the ROM Update:
  • Download and save the AT&T HTC One A9 ROM update file to your PC.
  • Connect your device to your PC via the supplied USB cable.
  • If the device is not recognized by the PC, ensure you have HTC Sync Manager installed and then disconnect and reconnect the device from the USB cable.
  • Once the device is properly recognized on the PC, locate the HTC One A9 ROM Update file that you downloaded. Double-click on the file to launch the system update wizard.
  • Follow all of the system update wizard instructions shown on your PC.
  • Once the update is complete, click Finish in the Wizard and the device will reboot.
  • Once the device reboots, the initial setup wizard will appear.
  • After the initial setup process is complete, open Play Store and tap the Menu icon, then select My apps and ensure all installed apps are updated.
  • After initial setup and updating all apps, the device is ready for use.

ROM Update Fails to Recognize the Device Solution

If the ROM update wizard fails to recognize the device, close the wizard and then follow the steps below:
  • From a powered off state, hold VOLUME DOWN while powering on the device to access download mode.
  • Connect the device to the PC while in this state and attempt the ROM update again.

To exit download mode manually, use the volume keys to navigate to reboot and press the POWER button to select it.

AT&T HTC One A9 ROM Update Download

(1.27.502.5) 6.0 Marshmallow ROM Update Size: 1.82GB Download