[Lenovo Zuk Z2 Pro Questions & Answers] juyer:
My story why I need an EFS or a radio image for Zuk Z2 pro ?

I've bricked radio/modem in my ZUK Z2 pro by hidden settings and „Set GSM/UMTS band” to USA band (only choice)

I live in Europe. I am a quite advanced user, I always root every phone.

Android Google play offered me to install an app „hidden settings”. I did.

There was a select radio band option. I clicked it just to check. In old MTK phones in engineering mode there were a list, like this http://www.cellphonemic.com/image/cache/data/B9500-band-500x500.jpg

But in new ZUK Z2 pro with android 6 there was a choice of USA band (only choice).

Something like this

http://attach.en.miui.com/forum/201608/23/031335orzj1vxxar1vymvm.png.thumb.jpg

It affected only the first SIM slot. Now my first SIM cannot connect - cannot send/receive calls and cannot send SMS. Changing to 3G and 2G gives me a no service. Changing to 4G gives me connection but only data works, cannot call, cannot send a SMS.

Many people have this problem after „Set GSM/UMTS band” to USA band (only choice). This is not a ZUK Z2 problem but Android settings problem.

IT'S STUPID that it could be undone. In OLD android there were a list:

"Automatic", "EURO Band", "USA Band", "JAPAN Band", "AUS Band", "AUS2 Band"

Method:

start an adb shell

type:

am start -n com.android.settings/.BandMode

works.

In new android there is only one entry "USA band".

I know people tried many things.

“Factory reset but that didn't help.”

“I did factory reset and nothing, I installed the factory image and either. “

I did for instance:

dd if=/dev/zero of=/dev/block/bootdevice/by-name/modemst1

Restart. No result.

It's very frustrating that the software will not allow me to reverse what he did.

Problem probably is here:

https://android.googlesource.com/pl....0_r26/src/com/android/settings/BandMode.java

Many people on many forums described this on many different phones and there is no solution.

One guy mentioned:

“Switch the phone to FLIGHT/AIRPLANE MODE (I did this by dragging down the top menu bar on my phone which is running a custom rom)

Press the menu key and SELECT RADIO BAND - you'll see the complete list of country bands - do NOT select a band yet....”

but it does NOT work for zuk z2 pro.

Zuk Z2 pro is no alone. One said: “Tks 4 ur guide !” but another “I try your trick,but not work in my device.”

One guy (Bitdomo's) made a custom rom for “nexus 5x” - instead of querying the baseband for available band modes just displays all six band modes. People were happy. “I flashed your ROM and then Phone Information had Auto in select band using which I switched back to GSM.”

https://img.xda-cdn.com/Lpw6Ao9fHG6...es.hu/151126/ffsafas_www.kepfeltoltes.hu_.png

or “ I resolved the problem by flashing Bidomo's ROM”.

But I don't have Nexus 5, I have Zuk Z2 pro.

So the only solution to change baseband is changing the source code of BandMode.java, compile and flash my own rom in the Zuk Z2 pro ?

Not cool Google.

There is probably also a second option:

“Well guys, if anyone else is having this problem now, there is an easier method. You can just restore your efs backup. Yes it's for root users only, but if you have it, it's as easy as rebooting to twrp and restoring efs then reboot without wiping anything.

Btw I have really no idea why google didn't implement an auto band option...”

But I don't have EFS backup...

some said:

“i just flash radio .img solved.”

I don't have radio.img for Zuk Z2 pro

Probably this setting has changed just a byte in a configuration. Does anybody have any idea where could it be ? Or any idea how to fix this baseband ?

Please help.

PS Fortunately second SIM card in my Zuk Z2 pro works. Strange, heh?