Guide to Upgrade ROM HTC One M9 (ACG).

Upgrade ROM HTC One M9 (ACG). This device Also known as HTC M9, HTC One Hima. By upgrading your Android phone, especially on HTC One M9 (ACG) smartphone. You will get many benefits on your Android phone. For an example your phone will get Removal of Bloatware, Performance Enhancement on your Android phone, Battery Life Enhancement for long usage, You will get Unified Experience, Ported Apps, Portable ROMs, Unique Experience and much more. Before we proceed to upgrade ROM on HTC One M9 (ACG), it is better we know whta is detail specification of this smartphone. HTC One M9 (ACG) device Available released on 2015, March, this device is the smartphone with 5,0 Inchi wide Super LCD3 capacitive touchscreen, 16M colors, work on Android OS, v5.0 (Lollipop), v5.1 (Lollipop), planned upgrade to v6.0 (Marshmallow) and supported with Quad-core 1.5 GHz Cortex-A53 & Quad-core 2.0 GHz Cortex-A57 CPU, GPU Adreno 430, combined with 3 GB of RAM and 20MP on main camera, and 4 MP on secondary camera..

On this guide not available for Verizon Wireless Devices. However select Verizon Wireless devices can be updated using the HTC Sync Manager software. So you must download HTC Sync Manager software Here. 

http://www.htc.com/us/software/htc-sync-manager/

Prerequisite.

1. Download HTC One M9 (ACG) ROM.

http://dl3.htc.com/application/RUU_HIMA_WHL_L51_SENSE70_SPCS_MR_ACG_US_2.11.510.16.exe

2. ROM  Versions.

2.11.510.16

Whats new on this ROM.

On this ROM provides the following key enhancements:

• N/A

Guide to Upgrade ROM / Firmware on Android HTC One M9 (ACG).

1. Make sure your device is HTC One M9 (ACG).
2. Make sure you have fully battery charge or at least you have 80% of battery capacity.
3. Make sure your HTC One M9 (ACG) device is connected to AT&T 4G/LTE or a stable Wi-Fi network
4. Make sure to confirm  that this software upgrade to 2.11.510.16 is a newer version than what is currently loaded on your HTC One M9 (ACG) device.
5. If your software version is the same with this version, just cancel to proceed this guide.
6. To check your software version you can go to ;
• All apps > Settings > About and locate the Software information.
7. Then, if your software version is less then 2.11.510.16 you should proceed with this upgrade.
8. Installation.
• On Line Installation.
• When your HTC One M9 (ACG) device goes On Line, you can download and install the update from the device.
• Go toHome screen then tap All apps , 
• Then tap Settings
• Tap System update.
• Then tap HTC Software update.
• Tap Check Now
• Now, tap Download 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 2.11.510.16
• Now your HTC One M9 (ACG) device  will reboot and begin installation.  
• The process will take approximately 10 minutes.
• Once the system update is complete, tap OK to continue.
• Attention: During upgrade process, your HTC One M9 (ACG) device will reboot multiple times. (this is normal) and software upgrade will show on screen. So, Don't do this on your device;
• Remove charger.
• Switch off device by press power button for long time.
• If you did it, your device might damage.
• Manual system update.
• Use this method to upgrade HTC One M9 (ACG) device will delete all data and information stored on this device. Make sure you backup all data before proceed this task.
• Use this method if you are outside of AT&T/Wi-Fi coverage or the update is not found on your HTC One M9 (ACG) device.
• Download and save the HTC One™ ROM update to your PC.
• Then, Connect your  HTC One M9 (ACG) device to your PC via the original 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 HTC One M9 (ACG) device is properly recognized on the PC, locate the HTC One™ ROM Update 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 HTC One M9 (ACG) 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.

Trouble shooting.

If the ROM update process fails to recognize the HTC One M9 (ACG) device, close the wizard and then follow this step below;

1. From powered Off state device, Press and hod Volume Down + Power Button  to access download mode.
2. Then, connect the HTC One M9 (ACG) device to the PC while in this state and attempt the ROM update again.
3. Once upgrade process finished, you can exit from download mode by using volume keys to navigate to reboot and press the Power button to confirm it.
4. Finish.