[Q] Baseband Unknown - Galaxy S II Q&A, Help & Troubleshooting

Okay here is the problemo
i was running D4v10 with siyah Kernel
I had the dreaded unknown baseband, Unknown Imei last night after my phone randomly rebooted. Thought Okay, ill restore it with helcats EFS tool. didnt fix it.
So next i tried to restore the EFS backup with http://forum.xda-developers.com/showthread.php?t=1308546. That didnt work either.
The phone has been factory reset
So i flashed KI4 generic from Intractech's stock thread and used CF root to go with it and it worked my Baseband and IMEI are restored, However now whenever i flash any new firmware VIA Recovery (GB roms, CM9 and AOKP etc) my Baseband and IMEI become unknown. so basically my phone still works if i use a stock firmware with CF root, but i cannot flash any new Roms via Recovery. Not even LP7 Generic works...
Has anyone come across any similar problems to this?

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Also Flashing the Ki4 stock firmware, Nandroid back it and then updating to CM9 doesnt work, however when i restore the backup it works again :S
tearing out hair

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i flash my sgs1 an sgs2 uncountable times but i din face pblm,but yes once my efs got corrupted in sgs1 but i had bckup......anyways wat u do first factory wipe,clear cache,cache prtition then do a clean install of stock rom tht ur kies shows not any otha stock,,,then use the correct cf root for rooting an for cwm...check if all is good then install hellcat and make a new image of efs(only if phone is all good)then will c later if ya got prblm

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rocky23 said:
i flash my sgs1 an sgs2 uncountable times but i din face pblm,but yes once my efs got corrupted in sgs1 but i had bckup......anyways wat u do first factory wipe,clear cache,cache prtition then do a clean install of stock rom tht ur kies shows not any otha stock,,,then use the correct cf root for rooting an for cwm...check if all is good then install hellcat and make a new image of efs(only if phone is all good)then will c later if ya got prblm
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yeah the EFS backup i have is fine. /EFS is also fine. The only way i can get it to work is if i use the KI4 stock firmware. Kernel choice doesnt even matter.

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tjjensen23 said:
yeah the EFS backup i have is fine. /EFS is also fine. The only way i can get it to work is if i use the KI4 stock firmware. Kernel choice doesnt even matter.
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yeah but the efs back up u must have taken wen the phone was good right,an ki4 its gb rom...so u can try flashing as i told an yes kernels do matter m8,cf root the right one later u can enter neak or redpill i don sujjest siyah new versions..an flash the desired rom

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Nothing but stock ki4 results in unknown baseband. That is the problem. No matter what I flash or how I flash it, results are the same.
I only managed to get it to work once with efs pro on a different firmware (lp7). The phone didn't reboot and and after a couple of minutes it was fine until reboot.
Sent from my MB860 using xda premium

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tjjensen23 said:
Nothing but stock ki4 results in unknown baseband. That is the problem. No matter what I flash or how I flash it, results are the same.
I only managed to get it to work once with efs pro on a different firmware (lp7). The phone didn't reboot and and after a couple of minutes it was fine until reboot.
Sent from my MB860 using xda premium
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ok so u have no imei prblm,signal, only unknow baseband,,,then y don u flash only modem on the rom ...an right now wat rom,kernel ur on??

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No the imei is also unknown. I've tried multiple different modems ranging from ki4 kl1 lpq etc
The only firmware in which it works is ki4 (haven't tried more gb firmwares yet though. Will tonight). Any ics or non stock gb firmwares haven't worked.
Sent from my MB860 using xda premium

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if the imei no is come to defaualt then efs is curropt don flash roms it wont work .once on my sgs1 wat i did was --delete the imei file in the efs folder in phone ,nv-data.bin,nv-data.bin.md5 and then i took these 3 files frm backup and pated in efs of phone,then rebooted an my csc,pcode,imei was back again ..many suggest flashing a stock rom,but tht dint work ,and the to restore csc well tht too dint work i myself expiremented and was back good again....

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tjjensen23 said:
No the imei is also unknown. I've tried multiple different modems ranging from ki4 kl1 lpq etc
The only firmware in which it works is ki4 (haven't tried more gb firmwares yet though. Will tonight). Any ics or non stock gb firmwares haven't worked.
Sent from my MB860 using xda premium
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Click to collapse
There's a known 'Unknown baseband' bug when you charge the phone and flash new roms. Take out the battery for 180 seconds. Put it back in. Go into recovery wipe cache, format cache, wipe dalvik cache. Reboot. See if it works.

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Will try when I get home and I'll post the results.
Sent from my MB860 using xda premium

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tjjensen23 said:
Will try when I get home and I'll post the results.
Sent from my MB860 using xda premium
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Click to collapse
So did it work? Having the same problem here.

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Reboot with no charger connected, issue solved?
If not, flash another modem (doesn't matter which one) and reboot (unconnected)
+1, known issue.
Tapatalked from my Samsung GT9100

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tjjensen23 said:
Will try when I get home and I'll post the results.
Sent from my MB860 using xda premium
Click to expand...
Click to collapse
-download modem here
-make sure your phone is disconnected from charger
-flash modem
-reboot phone
problem solved