I’ve been using a T-Mobile SIM card in both an AT&T and Verizon HTC One M8 for the past few weeks on their stock (but rooted) firmware. While both handsets are unlocked for use with GSM carriers, HTC’s implementation of APN and entitlement checks make it problematic at best to use all the features available. For example, MMS does not work on either device, regardless of APN settings, and attempting to tether invokes HTC’s Tethering Guard app to check if tethering is included as part of your data plan. This is fine if you have a tethering plan on the original carrier, but when using another carrier’s SIM card, the check fails. Turns out, the fix is a simple text edit of one of the carrier customization files found in the system folder.
Using a root enabled file explorer (I prefer Root Explorer, but ES File Explorer File Manager also has root access), browse to /system/customize/ACC/. Once you find it, long press on default.xml and select Open in Text Editor from the dialog box that pops up.
What you see once default.xml is opened is carrier specific settings for how certain HTC apps work. The apps are listed alphabetically so scroll all the way down near the end to “Tethering_provision” and note the value. If it is “1” this means Tethering Guard is enabled so just replace it with “0” and save the file. Once you have closed everything, reboot your phone for the new setting to take effect.
If you use Root Explorer, it will create a backup of the original file in the same folder in case you need to restore this. Otherwise, make your own back up of the file or just change it back in the future if needed.
That’s all it takes. Once completed, you are able to natively tether using any SIM in the carrier branded HTC One M8.
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