I using Sony Updates software for upgrade it, previous purpose only to making backup Stock ROM, then my root access was gone.
I combine many posting to gain back root access, actually my FW was Indonesia CDA, it may be broke warranty, but I try replace 2.257 with 1.510, that still rootable, with same interface (like white theme on setting). I just wanna share what I simple done.
1. Flash your device with previous FW( Me, use Indonesia 1.510), for you please select as you wish. Download it first.
All official Rom for C6802
Using FlashTool to up
A: Sony Xperia Z Ultra/XL39h/C6802_14.1.B.0. 461 (Hong Kong Version)
https://mega.co.nz/#! EhZzDbBY! UduW6zCUdnodSBNM0OhAsynyStx428MlB4gCA700UYU
H: Sony Xperia Z Ultra/XL39h/C6802_14.1.b1.526 HK
https://mega.co.nz/#!BghDjKyT!ZsVS0VG9jqL3TMN5Xya7A2DFKdkKq-G015PGaDWr2TU Thanks: m3dd0g
J: Sony Xperia Z Ultra/XL39h/C6802_14.1.B.2.257 (HK)
2. Then, download Flash tools and flashing your device as tutorial below
3. Root it with Vroot
Just sucessfully rooted my ZUltra using the VRoot tool. Am running 510 fw (Indonesian C6802).
Just wanted to hare my steps:
1. Connect your phone (don't forget to enable USB Debugging)
2. Open the Vroot tool, wait until it detects the phone.
3. Click on the green button on the right bottom corner of the tool (root).
4. After sucesssfully root using the VRoot (your phone will reboot), install the SuperSU from playstore.
5. Open the SuperSU app, it will ask to update binary, click ok.
6. Then open the Vroot tool once again, click the white button (unroot) on the left of the green button, hence removing the chinese superuser app.
7. After that go to SuperSU -> Settings -> Install SuperU into /system.
8. After that reboot the phone, and the SuperSU will still be there, all apps requiring root works perfectly.
Note: if you cannot find the developer options in the settings to enable USB debugging (just like I did the first time ), go to About Phone and click on the Build Number menu 7 times. That will enable the developer mode.