[Xperia Z1 General] wdpt:
Addition for people who has problems with baseband

Kind of a necropost, please forgive me for that. If I knew the right drill, it would have saved me at least a weak of experimenting with ROMs. Also there is an easier way to do what OP did.

My guide is composed of SOL23 Japanese thread on 5ch.

(no links allowed, so look for 【ROM焼き】KDDI Xperia Z1 SOL23 root3)

and my own experience.

Goes without saying that you should backup everything, as we are going to wipe the freaking memory.

Also, read first - then act. Some actions are easy for me on a Linux machine (unpacking partitions from ftf file for example), you might just copy the files from your current ROM.

Given:

SOL23, KDDI, rooted. Bootloader locked.

ROM version does not matter, as stock ROMs are available

ftf andro plus

Goal:

Use full bandwidth of SOL23. If you flash global C6903 ROM, it will render the phone useless on most providers inside Japan (mine are Au/UQmobile, would not even connect after flashing)

If you already have the KDDI ROM installed and working fine, then backup /data/data/com.providers.telephony/database/telephony.db. Also go to /system/etc/firmware/ and copy files modem.b00 to modem.b26 plus modem.mdt. It has to be 21 file in total. You will need them later. Also you might just exclude BASEBAND and PARTITION when flashing global ROM, instead of reflashingthem atop.

IF you want to go from scratch -

You will need newest KDDI ROM for SOL23 (it is 14.3.C.0.300), downloadable on the page above. Actually any will work, but it is said that energy efficiency is better on the newest one, personally tested .81/.95/.239/.300 and all of them worked.

Also you will need any global stock lollipop ROM of your choice, personally used Customized DE and Customized SG 14.6.A.1.236 downloaded by ExperiFirm. Prerooted zips are also OK.

First you flash the your Global ROM with Flashtool. Boot into it. As soon as the first boot is finished and desktop is displayed - turn it off and flash BASEBAND and PARTITION from KDDI ROM. Content should be: amss_fsg.sin, amss_fs_1.sin, amss_fs_2.sin, partition.sin. NOTE: sometimes partition.sin is called differently, partition-image.sin for example. It is only the partition table, which will give you back your 32GB of memory. If unsure - look at the size of the file, it has to be tiny - tens of kilobytes.

You can also check the boxes "wipe APPS_LOG and USERDATA", but it went fine without checking them for me. It will wipe it anyway as the memory is re-partitioned.

Now boot into the system. It is gonna take a while - 15 minutes or so. Then you will be greeted with clean phone. Recovery and SuperSU will not disappear after flashing partition.sin.

Now you should be able to use 3G, but not LTE. We need some files from KDDI ROM. Extract /system from .TFT, go to /system/etc/firmware/ and copy files modem.b00 to modem.b26 plus modem.mdt. It has to be 21 file in total, as some modem.b files are missing.

Copy them with root explorer to the same location (overwrite existing files) on your phone and set rw-r--r-- permissions to them.

Now editing our build.prop, so SOL23 can shine in all its glory :cool: (also saves you from network losses apparently)

ro.semc.version.cust=1275-6766
ro.semc.version.cust_revision=R21C
ro.somc.customerid=6565
[B]ro.product.brand=KDDI [/B]
ro.semc.product.model=SOL23
ro.semc.ms_type_id=PM-0470-BV
ro.semc.version.fs=KDDI-LTE
ro.semc.product.name=Xperia Z1
ro.semc.product.device=C69
ro.product.model=SOL23
telephony.lteOnCdmaDevice=1

Line in bold needs to be added, everything else is just an edit.

Almost here. Restore working telephony.db from the backup, OR just add the APN of your provider by hand. You might need to put the phone to LTE only mode and reboot for the option to appear. Also sometimes it gives an error (not permitted to set APN name) the first time you add the APN, but second time works fine. Some weird issues were reported by a user from Au Mobile, when he switched carriers, resolved by cleaning "carriers" table in telephony.db with SQL editor and adding new APN manually.

Finally dial in *#*#4636#*#* and set the following:

Preferred network type: LTE/CDMA auto (PRL)

BY NOW IT SHOULD HAVE WORKED, they said.

AFAIK the next part is carrier specific. For me at this point it was possible to use LTE DATA and SMS, but calling directly would always fail. At the same time others were reporting no issues.

I solved it by changing the radio band in *#*#4636#*#* menu (3 dots on the top right -->>Select Radio Band) to "Cellular (800-MHz Band)"

and setting to TURN OFF IMS REGISTRATION REQUIRED in the same menu.

Also you might try different bands and settings. Good luck.