How to Jailbreak Iphone 3g 4.2 1 Baseband 6.15.00

Edit 2013-04-26 by PierreP: Try first the Whited00r tutorial - Downgrade iPad Baseband on iPhone 3G to Unlock which includes a custom firmware that let's you skip the steps 1 & 2 below. If it fails then follow steps 2, 3 & 4 below which worked absolutely fine for me on several iPhone 3G running iOS 3.1.3 or iOS 4.2.1 and impossible to carrier unlock Modem Firmware (a.k.a baseband or bb) 05.15.04 using my laptop running Windows 7 64-bit.

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If your iPhone 3G is running with > Settings > General > About > Modem Firmware: 05.15.04 or 05.14.02 and your SIM is working with cellular service then you have a Factory Unlocked device or the original SIM so you do not need this tutorial!

If your iPhone 3G is Factory Unlocked, you do not have to upgrade/downgrade your Baseband 05.15.04 because the point of this process is to be able to carrier unlock it to be able to use SIM's from any cellular provider. Just follow the instructions here: Whited00r Installation Tutorial and install Whited00r Normal Version.

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All other users, follow the tutorial below to free unlock your iPhone 3G on Modem Firmware 05.15.04 or 05.14.02 (a.k.a. Baseband or BB).

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HELLO WORLD!

Here is my tutorial on how to upgrade and downgrade your iPhone 3G and free carrier unlock it if you're stuck with the impossible to unlock 05.15.04 or 05.14.02 baseband:

Free Software we will be using on a Windows computer:
- sn0wbreeze 2.9.6 - custom firmware creator
- redsn0w 0.9.6rc16 - for upgrading locked baseband 05.15.04 to the unlockable iPad baseband 06.15.00
- redsn0w 0.9.14b2 - for downgrading iPad Baseband 6.15.00 without GPS to iPhone baseband 5.13.04 unlocked and perfectly working GPS
- the official iPhone iOS 4.2.1 firmware
- iREB r6 for Windows (more stable than the current iREB r7) & [f0recast. A new iREB for Mac is available.

1. Use sn0wbreeze 2.9.6 to create a custom firmware based on the official 4.2.1.
1a. Start sn0wbreeze and hit OK
1b. Click the arrow, browse for the 4.2.1 official firmware, click the arrow
1c. Click Expert mode
1d. Click General and hit the arrow
1e. Check all the options and leave the root partition size as it is and hit the arrow
1f. Check install iPad baseband and hit the arrow
1g. Custom boot logo (as you wish), hit the arrow
1h. Skip the custom apps, hit the arrow
1i. Select Build IPSW and hit the arrow
1j. The waiting game (stick with the spinner or play PacMan)
1k. After it's done it will guide you to put your phone in DFU mode.
1l. With your phone in DFU mode start iTunes and on the iPhone restore Shift+Restore and select the sn0wbreeze firmware saved on your desktop.
1m. It should start restoring your phone. (another waiting game)
1n. After the process is finished you should go to Settings > General > About and at the bottom there should be Modem Firmware: 6.15.00

2. ***only for those who still don't have the iPad baseband 06.15.00 after step 1 | the rest of you go to step 3***
2a. Connect your iPhone to the computer. Hold the lock button and swipe to shut down the phone.
2b. Open redsn0w 0.9.6rc16 (if you're using Windows Vista/7/8 right click it and Run as Administrator )
2c. Click Browse and select the official 4.2.1 firmware. Wait and click Next
2d. From the list deselect everything and select only Install iPad baseband and click Next
2e. If you know how to put your phone to DFU mode you can do it right now, if you don't click Next and follow the instructions
2f. With the phone in DFU mode redsn0w will start to update the baseband. (yes...another waiting game)
!!! DO NOT DISCONNECT THE PHONE DURING PROCESS !!!
2g. Phone reboots and you should have the baseband 6.15.00 at Settings > General > About

3. Using redsn0w 0.9.14b2 (Windows) to downgrade Baseband 06.15.00 to 05.13.04
3a. Shut down the phone again
3b. Start redsn0w 0.9.14b2 (if you're using Windows Vista/7/8: right-click redsn0w.exe and Run as Administrator )
3c. Click Extras > Select IPsW > browse for the 4.2.1 official firmware > OK > Back
3d. Click Jailbreak > *preparing jailbreak data* > select ONLY Downgrade from iPad baseband > Next > Put phone in DFU mode or follow the instructions for that
3e. Yey! Another waiting game!
!!! DO NOT DISCONNECT THE PHONE DURING PROCESS !!! It could take up to 10 minutes to complete.
3f. iPhone reboots and here you go! Now you should have the 5.13.04 baseband at Settings > General > About > and scroll down to Modem Firmware (a.k.a. baseband).
3g. If the Modem Firmware field is blank: turn off the iPhone, wait a couple of seconds turn on and do it again. If the data is still blank after restarting twice then follow the Restore to iPhone OS 3.1.3 chapter in the Whited00r tutorial - Downgrade iPad Baseband on iPhone 3G to Unlock

4. Use the free iREB to put the iPhone 3G in iReb PWNED DFU mode before using iTunes to update to the Whited00r 6 firmware and prevent iTunes errors 1015, 16xx, 1600, 1601, 1602, 1603 & 1604. You can also use iREB if you are stuck in a Recovery Mode Loop after flashing Whited00r:

After all this trouble you can now install Whited00r 6.0 Unlocked version by following the Whited00r Tutorial - Installation - Whited00r will not change your new Baseband!

And don't forget to reboot twice before making any modifications to the iPhone as explained in the tutorial and set the iPhone as New in iTunes.

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Original post:

Hello world!

So...it's been 3 days since i'm trying to install whited00r on my iPhone 3g with no luck.
I have an iPhone 3G running iOS 4.2.1 on baseband 05.15.04-6.4_M3S2 (tinyumbrella info).
The software that i used: redsn0w_win_0.9.15b3, iREB-r6, tinyumbrella-6.01.01 and the firmwares: iOS 4.2.1 iPad Baseband, iOS 4.2.1 official, whited00r 6.0.

Following the tutorial on whited00r web page did not help me. After i install whited00r 6.0 i can't get any network and signal to my phone. So after some searching i found that my baseband can't be unlocked so i have to upgrade to iPad baseband and after that downgrade.

So here's the big problem.
If i install using iTunes the firmware that you provide in tutorial (iOS 4.2.1 iPad Baseband) still no network or signal for my phone and in Settings > General> About the baseband is the same 05.15.04.
Trying to install the iPad baseband using redsn0w dosn't work. I selesct the 4.2.1 official firmware, i hit jailbreak, in the list i only check install iPad baseband, put the phone in DFU mode, it loads the ramdisk etc., but my phone remains on a black light screen (no info, no pineapple logo no nothing) and the process fails. Tried this several times.
I did a fresh install of my windows system run the process again managed to get it work on the phone, but after the redsn0w finished and rebooted my phone it got stuck at the apple logo.
Now i'm back to the black light screen and nothing seems to work.

Any idea on how to make it work?

Thank you.

PierreP Moderator edit: did some formatting, added some links & images.

How to Jailbreak Iphone 3g 4.2 1 Baseband 6.15.00

Source: http://www.whited00r.com/forum/index?topic=7134.0