[OnePlus 6T  Guides, News, & Discussion] snake2332:
Can someone help me? I got a T-Mobile (I think) version of the 6T. It's glossy black on the back and the SIM tray only has 1 spot, so I think that's the T-Mo version right? Well, it has the internation ROM version 9.0.17 on it. I am a T-Mo customer and want to revert it to the T-Mo ROM because my battery life has been whack (sometimes using as little as 1.7%/hr in standby, but often 8%/hr with no extra features enabled like voice detection, tap to wake, etc.).

So I got the MSM tool and proceeded to follow the instructions. My phone doesn't do anything when I hold vol + and - and plug in the USB cable - it remains powered off. It doesn't do anything when I push vol + and - and PWR either, or any other combination of buttons. After attempting this, I turned on the phone normally and it booted into safe mode with black and white icons. Well, I had previously enabled the advanced power menu so I simply rebooted the phone into fastboot "bootloader". On my PC, it comes up as Other -> Android in Device Manager. I tried both versions of the Qualcomm USB drivers. I forced the device to look for drivers in C:\Program Files (x86)\QUALCOMM Incorporated\Qualcomm USB Drivers For Windows\DriverPackage\Qualcomm\ but it finds none. I also tried both WWAN and ETHERNET during the driver installations.

My phone is sitting at the FastBoot Mode screen. It shows:

FastBoot Mode

PRODUCT_NAME - sdm845

VARIANT - SDM UFS

BOOTLOADER VERSION -

BASEBAND VERSION -

SERIAL NUMBER - [it has a serial # that looks legit]

SECURE BOOT - yes

DEVICE STATE - locked

Any ideas what might be wrong with my device? I can boot into recovery and fastboot modes but fastboot drivers aren't working. PC is Win10 64bit build 1709.

Thanks!

UPDATE:

I followed suggestion at https://xdaforums.com/oneplus-6t/help/help-op-6t-recognized-fastboot-t3874694, using the Google drivers. Those didn't work either. However, when I attempted the "hold vol + and - while plugging in the USB cable" with no Qualcomm drivers installed, the device came up as Other -> Qua-something, but the phone display never showed anything and it was stuck powered off for awhile (no USB plugged in) until I think eventually vol - and pwr worked to turn it back on. Felt like it was bricked for awhile, haha.

Anyway, I got the 9.0.16 version of the MSM tool and am prepared to use it. So I rebooted phone into Fastboot mode via the power menu again, with no Qualcomm installed on my PC, plugged in the phone, and it comes up as Other -> Android again. Google USB drivers don't work, neither do the Qualcomm ones. I'll keep searching for answers...

---------- Post added at 06:48 PM ---------- Previous post was at 06:25 PM ----------

Oh I found the T-Mobile thread talking about using this MSM tool from Dark Nightmare. Sorry if I posted in the wrong thread by posting here.

Just wanted to say that I got the phone to show up as COM7 in MSM by booting into Fastboot via power menu, then choosing POWER OFF, hitting PWR to go, then holding vol - and + while the 1+ logo was on-screen. It popped up in Device Manager properly now, but the display is black on the phone. Regardless, I tried running the MSM tool for v9.0.16 but it errors after 4 sec saying the image mismatched or something. I realized I should get the MSM tool from the T-Mobile thread that Dark Nightmare started. Downloading that now while my phone is still connected as COM7 despite showing nothing on-screen. Is that normal for it to be black for this process?

FINAL UPDATE:

The MSM tool from the proper T-Mobile thread worked. I don't know what the issue with the drivers was, but it's working now. The phone remains black during the flashing, but it looks like it's working. Sorry for posting in the wrong thread. I would delete this entire post if it let me.