I have been warning people for some time now against upgrading your baseband Modem Firmware to 6.15.00 to unlock 3G/3GS iPhone’s with ultrasn0w. This causes the 3G/3GS iPhones GPS to fail.
Beijing iPhone Repair has reported in some cases 6.15′ing your 3G/3GS iPhones can cause Bluetooth and IMEI failures so that the iPhone is bricked.
I do taken in on trade 6.15′ed iPhones but when I sell them I inform the buying of the problems and give them a discount on the 6.15′ed iPhone. In my opinion you should refuse to have your iPhone’s Modem Firmware updated to 6.15.00. I have so far always refused to 6.15 a 3G/3GS iPhone.
In fact have been warning people against 6.15′ing 3G/3GS iPhones for some time now and here are the reasons why.
1. Always Have To Use Custom IPSW To Restore — Once you flash the baseband to 06.15.00 you can never restore the offical iOS software again and if you do it will put your phone into a recovery loop which requires hacker tools to recover from. Any time you want to update the iOS software you will need to use a jailbreaking utility like sn0wbreeze (PC) or Pwnagetool (Mac) to restore a custom created IPSW file.
Here is the 7 step process to restore or upgrade a 6.15′ed 3G/3GS iPhone so it can be unlocked. I charge $30 to do this. Most people will not be able to do this even with the instructions in front of them.
2. Reseting A 6.15′ed iPhone Bricks It — When a Jailbroken iPhone is Reset (Settings–>General–>Reset) it will cause the phone to brick and you will need to Restore. If the iPhone that was Reset is 6.15′ed then it will need to have a Custom IPSW Restored using this 7 step process.
So here is what happens. You sell the phone and the person goes and Resets the phone so all your info is erased and the phone is bricked. I had this happen and the person that bought the phone from me freaked and accused me of selling them broken phone and was so mad they couldn’t even listen to what I was telling them. What a mess that one was. They even threatened me.
3. Voids Warranty — It will void any warranty that you have with Apple. This is not an issue like Jailbreaking where you can restore your iPhone to the original iOS. Once you 6.15 your iPhone you can’t go back.
Check your iPhone warranty by selecting the Check Your Service & Support Coverage link on the Apple Support page.
4. Breaks GPS — In all cases it breaks the phones GPS. There is a difference between a GPS app and a GPS-A app. The iPhone Maps app will still work using GPS-A but a GPS app like TomTom will not work.
5. Can Break Bluetooth & Permanently Brick Your Phone — In some cases it can also break your Bluetooth, erase your IMEI number, and cause yoru baseband chip to fail. http://www.beijingiphonerepair.com/fix/no-imei-no-bluetooth-and-no-wifi-error-on-iphone-3g-or-3gs-is-due-to-baseband-chip-failure/
6. Devalues Your iPhone — It devalues your phone to those who know the above points.