@tonsofquestions did you find anything interesting using the modem access I have hinted you with?
I am asking if you happened to know if it was possible to unlock some LTE bands.
I just happen to be the unlucky one to get Japanese version of xz1c motherboard and I wonder if I can make it work with LTE band 20.
Unfortunately, not yet.
I had some work and travel for part of the holidays - and then got suck by weather/airport delays. Since I didn't have my tools, I was unable to experiment with backing up and restoring my phone yet.
Looking at the link again, it seems like this might actually be an app I could install - but I'm not sure how to build it. Last time I thought it was just a module built in to LOS. Or am I misunderstanding?
I'd be happy to try installing it on my current ROM, if you think that would make sense. Otherwise it might have to wait until the new year.
My previous understanding was that the hardware itself on the Japanese motherboards were different; I feel like I've seen posts about people installing the US ROM images on them, but it still didn't work. But I might be misremembering.
@tonsofquestions I am afraid that the OpenCustomizationSelector cannot be just installed as an app, it needs other supporting stuff in the rom to work, so you would need to test it with LOS.
I have posted more info about the diag mode into the previously linked los devonly thread, including info to enable diag mode in los itself - possibly could work with other custom roms too.
Interesting, thanks for this info! It at least explains why I was unable to get into it, despite the Qualcomm modem.
Do you have any experience with the "setprop persist.usb.eng 1" setting, and what it's doing?
As far as I can tell that's sometimes doing triggering a similar mode for folks, with some ROMs, but I don't understand it enough to grok why it's not doing the same for my device, and if it's even possible to get it working or if I need to switch to a completely different ROM.
It seems like the modem configuration should be independent of the ROM, but I have a sneaky suspicion that backing up, switching/re-configuring, then restoring my current one won't end up with it working any better.
Do you know anything about which operations are or aren't possible? The Xperia 1 III post suggests that some of them are possible - at least to download and upload files, which is hopefully enough here to tweak my settings so I'd have better LTE/VoIP compatibility.
concerning EDL mode (as discussed a different thing to diag mode) - you can boot into EDL with retail xz1c using a kernel patch which re-adds support for 'adb reboot edl', but it is not useful, because it needs sony signed EDL image that is loaded via usb (I happen to have it, but all interesting commands are protected by sony authentication, so it is not useful anyway)