DESCRIPTION

If you bricked your Lenovo TAB 4 8 Plus while  trying to Root it or to install TWRP on it, then you will certainly be able to get it up and running with one of the methods below.

The two files  SuperSu working on Lenovo TB-8704F  and  TWRP-3.4.0-0_TB-8704F.img for Lenovo TAB 4 8+, will furthermore produce the results you were after.

Once you're the happy owner of a Lenovo that is up and running again, please let people know that it worked for you in a comment.

You may need to install ADB and Fastboot

Except for Qfil below you need ADB and Fastboot. People who bricked their device already have this installed, but in case you need it: Download and install minimal_adb_fastboot_v1.4.3_setup.exe (see link above). All statements below assume that  the resultant installation's path C:\Program Files (x86)\Minimal ADB and Fastboot  is added to your Path environment variable. In order to add this please follow these simple steps: https://www.architectryan.com/2018/03/17/add-to-the-path-on-windows-10/

For using Fastboot you will find the statements needed in the text below, so you need no study. But if you insist to know more, there are many sources e.g.:  https://www.techrrival.com/flash-recovery-adb-fastboot  and/or  https://forum.xda-developers.com/showthread.php?t=2317790.

In case you need USB drivers for your Lenovo TAB 4 8 Plus you can get them on this page: https://androidmtk.com/download-lenovo-usb-drivers

NB: If you restored your device and need ADB 'to see' your up and running device via USB, set USB connection mode to  MTP  (settings/system/developer options/Select_USB_Configuration)

Explanation of the contents of the Files and the different methods to unbrick your device

*File1:  Unbrick by FASTBOOT flashing BOOT.img and/or RECOVERY.img for devices that were on Android 8

If you were on Adroid 8  and  Fastboot mode  is still accessible (hold Vol- &  PowerKey until vibration), then you can directly Fastboot flash BOOT.IMG and/or RECOVERY.IMG to it (instructions below).

* Bricked by wrong SuperSu (in Android 8):

If your boot loader got ruined by inadvertantly installing a non functioning SuperSu version, you would restore it by flashing BOOT.IMG which you unzipped in say  c:\download. To do this, start the tablet in fastboot mode (hold Vol- & PowerKey until vibration), connect it to your computer via USB. Open a Poweshell on c:\download (in Explorer, hold shift key and right click on c:\download then choose Open Powershell window here). In Powershell issue the command:  fastboot flash boot boot.img

* Bricked by wrong TWRP (in Android 8):

Same procedure as above, except now issue: fastboot flash recovery recovery.img

NB, Got bricked in Android 7 ? Use QFIL below

in case you got bricked while in Android 7  you can't use these BOOT.IMG and RECOVERY.IMG since they are not compatible with the Android 7 SYSTEM, so your tablet would stay bricked. First try to find the Android 7  .img files somewhere and if you do not succeed then use the QFIL method  below.

*File2: Ubrick with QFIL (resulting in factory Android 7.1.1, which gets the Oreo OTA update)

If you can't get your device in Fastboot mode, you can use the QFIL route. Download QFIL from here: https://qfiltool.com/category/download .  Note that the Qfil procedure will result in a factory reset.

You need a Qualcomm USB driver and a userguide  which you find here: https://androidmtk.com/use-qualcomm-flash-image-loader-qfil  (or if you only need the Qualcomm USB driver, you can download the qualcomm_driver.zip from the link above).

I uploaded the source files for use with QFIL , as LenovoTAB4-8Plus_QFIL_Android7.1.1.zip. The  resultant Android 7 will after installation notify you about an OTA update to Oreo.

To enable your device to communicate with QFIL, a (soft) COM port needs to be assigned to it. Connecting your device to USB (MTP mode) will automatically create that COM port if  you hold down the volume+ key while connecting it. In case you get the 'USB device not recognized' message, reboot in Recovery ( press/hold vol+ and Power keys) and choose 'power off' from there.

In Qfil, press 'Select Port' and select your device. Choose 'Flat Build'  and then  the 'Load XML' button. The extracted zipfile contains a folder named Romfiles. Navigate to that folder and find and select  rawprogram_upgrade.xml and then patch0.xml. Now click 'Browse…'  and click the only .mbn file you find there. Then press 'Download'. A blue download progress bar should now become active. However, if  -as it happens on some computers- the download process won't start, so the blue progress bar does not become active, or when the infamous 'Sahara Fail' error appears in the Status-window: quit Qfil, restart it, goto menu item 'Configuration/FileHose Configuration' and tick 'Max Payload Size to Target in Byte' . Then press 'Download' again. Wait till Qfil has finished.  Press and hold Volume+ and Power buttons until vibration  to reboot into Recovery and boot the system from there (please be very patient at the first boot, since you can easily  get the impression that your tablet got stuck….).

If you do not automatically get notifified about the Oreo Update, goto: Setup/About Tablet/System Update/Download and start it from there.

*File3:  Unbrick with a TWRP backup taken from a 8704F that got an OTA_update (security update Android 8.1.0 – nov '22)

Using File3, you can also unbrick via a TWRP/Restore if Fastboot mode  is still accessible (hold Vol- &  PowerKey until vibration) . This is a TWRP backup without /DATA of an Android 8.1.0 system, OTA updated on nov 2022 (when I found my Lenovo flagging an OTA -security- update). Note: If you ever encounter a new update yourself, it will 'refuse' to install with TWRP as Recovery, since it needs the stock Recovery, so you could temporarily flash recovery.img.

Since this TWRP backup does not contain a backup of the /DATA partition, if your tablet's /DATA is still intact then, after finishing the TWRP/Restore you will find your account and installed apps and stuff exactly as before you bricked your tablet. 

Procedure: Download and extract zip File3  above to  c:\some_folder.  After extraction, c:\some_folder contains the directory TWRP which directory, after copying it to your internal storage or SD card will be recognized by TWRP .

To install TWRP recovery, use the TWRP-3.4.0-0_TB-8704F.img from File4 above. Download and extract that version to your c:\some_folder. Open a Powershell on c:\some_folder (in Explorer, hold shift key and right click on c:\some_folder, then choose 'Open Powershell window here') and  issue: fastboot flash recovery  .\twrp-3.4.0-0_TB-8704F.img. Reboot the tablet in TWRP Recovery (press/hold the Vol+ and Power buttons until vibration). With TWRP booted, your tablet will now become visible in Windows Explorer as 'Portable Media Player'. Double click this, then doubleclick the location you want to have the TWRP directory (internal Storage or MicroSD) and copy the extracted directory TWRP there.

On your tablet in TWRP, press Mount and see to it that 'Mount system partition read-only' is Not ticked.  Press Select storage and choose the location of the just copied TWRP directory, OK, Back, Restore and select  the 8704F_S001018_191009_ROW backup. Then tick everything you see. However, you could choose to untick RECOVERY, if you do not want to end up with stock recovery after the restore. Now do the Swipe to Restore.

After a successful restore, reboot, but please be very patient at this first boot (!) since you can easily be tempted to think that your tablet is still stuck….

Note: TWRP can also be used without installing it !      Just issue fastboot boot  .\TWRP-3.4.0-0_TB-8704F.img. The only drawback I found is that using the Reboot button in TWRP now hangs the system. Not a real problem, but you always have to restart using the Power/Vol keys.

*File4  Working TWRP recovery for Lenovo TAB 4 8 plus

Version: TWRP-3.4.0-0_TB-8704F.img for Lenovo TAB 4 8 Plus 

This version works flawlessly. See 'To install TWRP recovery' under the heading *File3 for instructions.

*File5 Supersu for rooting Lenovo TAB 4 8 plus (for Unrooting download SuperSU-Uninstaller.zip see link below)

Rooting: Download and copy File5 UPDATE-SuperSU-v2.82-20170528234214_working.zip to your internal storage or SD card and then use TWRP/Install on this .zip file. (Supersu source from here: https://www.thecustomdroid.com/download-install-supersu-zip-root/)

Unrooting: Goto  https://www.cararoot.com/supersu-uninstaller-en/#download,  download and copy the zip file to your internal storage or SD card and then use TWRP/Install on this .zip file.  This installation tells you to restore BOOT.img If done. In a Powershell on a directory where BOOT.img lives, issue:  fastboot flash boot boot.img (if desired, see detailed explanation above under *File1)

Have fun and please leave a comment if you're happy with your now functioning tablet !

Some problems and solutions

Once in a while I encounter this error message in TWRP while trying to restore a backup:

Failed to mount '/data'. If you plan to restore /DATA then you can use this advice I found and followed: What you need to do before restoring is remove Crypto on Data. To do that, in TWRP

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Additional info

- File1 for Fastboot:flashing. img files  are  from Android 8.1.0

Build number TB-8704F_S001011_181108_ROW

Software version TB-8704F_RF001_170517

- File2 for use with Qfil resulting in  Andorid 7.1.1

Build number TB-8704F_S000037_180096_ROW

- File3

Build number is:  8704F_S001018_191009_ROW),

※Please make a backup of your device before installing or updating ROM