[Galaxy S II General] Hopper8:
This guide is provided for information only. I will not be held responsible if you cause any damage, software or hardware, to your phone by following the guide. You are choosing to follow this guide, and as such, you choose to accept any responsibility for any mishap that may occur.

WARNING: Do not follow this guide if you think (or even suspect) that your USB port may be faulty in any way (ie, slow charging, loose connection among other faults). If your USB port is faulty, it must be fixed before flashing, or you are in danger of hard-bricking your phone. If the connection to the computer fails even for a moment, at best the flash will fail, and at worst the phone will need a new motherboard. Either send it to a service centre, or here is a good place to start if you want to DIY.

WARNING #2: If at all possible, make sure you have a backup of your efs folder (using Hellcat's app, "kTool" from playstore). Efs is the folder which contains your imei. No imei =no signal. Flashing a ROM may corrupt the efs folder, in which case the backup will be invaluable. If you do not have a working backup of your efs folder, I am not responsible if you choose to follow this guide and your efs becomes corrupt.

Symptoms

This guide is for people who find themselves in the situation where:

The phone currently will not boot.

The phone can only enter download mode (If it can’t do that, see the section below.)

If, for whatever reason, an Odin flash fails.

It assumes you know the basics of Odin flashing. If not, see here.

No download mode?

If your phone won’t enter download mode, you can try three things:

A USB jig. Don’t pin your hopes on this, they rarely succeed in this scenario.

‘Jump starting’ – You might need someone else to give you a hand for this. Take the battery out of your phone and wait 30 seconds. Now, press the button combination to enter download mode, and with this combination still depressed, get someone to put the battery back in. Hopefully this will jolt your phone into download mode.

Take out the phone battery, and re-insert it, but don’t turn the phone on. Now, plug in the charger while holding the volume down button. Keep holding volume down till you enter download mode.

If your phone won’t enter download mode, and will do nothing but get hot when you attempt to do anything to it (charge it, turn it on), then your motherboard is in need of replacement.

Your options

I’ve seen a lot of people, when their Odin flash fails, either:

Give up. Not a good option.

Flash a .pit file. That should be used as an absolute last resort. There’s a lot to try before getting to that stage! If a flash of a .pit file fails in Odin, your phone is well and truly unrecoverable, and you will need a motherboard (MB) replacement.

Send their phone to a service centre. That costs money (& you’re without a phone for a week or so).

Read on and hopefully you will be able to recover your phone without spending anything.

What to do

Keep flashing via Odin. You don't really have a choice. As for the files to flash: It’s worth trying to flash a range of stock ROM’s and custom kernels. I recommend downloading a stock firmware from Samfirmware for your device; either ICS 4.0.3 or JB 4.1.2. Stay away from 4.0.4 (research emmc brickbug if you’re interested.) See here for the stock ROM’s. Alternatively you can also download firmwares from xda. Make sure you’re using the correct firmware for your device variant and region (i9100, i9100g, i9100p etc).

As for custom kernels: If you manage to flash a custom kernel onto your phone, that gives you recovery (usually CWM for i9100), from which you can either restore a nandroid backup, or flash a custom ROM. ONLY for i9100: See here for Siyah kernel. If you were previously on ICS, flash ‘siyahkernel s2-v5.01’ from that link. If you were previously on JB stock, flash the ‘S2-v6.0beta5’. You want the .tar extension in both cases. If you were on a 4.2.2 or 4.3/4.3.1 ROM, see here. You want the file called "Kernel_Dorimanx-V9.43-[12-16]-[24-10]-TAR-FOR-ODIN.tar". None of the other files downloadable from that mirror are Odin-flashable. All files linked are for international I9100. Even still:

Your best bet is to continue to attempt to flash Stock ROMs for your model variant and region.

Another option for i9100

If you have an i9100, probably the best option to flash is to flash 4.1.2 JellyBean leak. Huge thanks to It_ler for providing the file after it was lost during the shutdown of hosting site hotfile.com and re-hosting on his dev-host, and for keithross39 for re-hosting the file on his storage. Download it here: (Android File Host link) or here: Mega link. This is a 3-part firmware. It will wipe your device as it flashes, and in many cases this extra wipe while flashing contributes to a successful flash. To set this file up in Odin (as it is 3 parts): PDA = CODE_I9100XXLSJ.tar, PHONE = MODEM_I9100XXLS6.tar, and CSC = CSC_HOME_OXX_I9100OXXLS1.tar. As usual, do not tick 'repartition'.

Now that you have chosen a file to flash, continue on.

If Odin won't recognise the phone ...if it does, continue to 'Preliminary Steps'

Firstly, keep trying. Many users will find that Odin will recognise the phone in download mode eventually, but this will take perseverance. Note that if you do get Odin to recognise your phone in download mode, attempt to flash a stock ROM then. Don't unplug it thinking 'you'll try again later'.

Things to try if the phone isn't recognised by Odin:

Open Odin without the phone plugged in. Enter Download mode without the phone plugged in. Now, plug the phone in and wait a few seconds.

Didn't work? Try again in a different USB port. Still didn't work? Try all the USB ports, and then a different computer. If that doesn't work:

Uninstall the USB drivers using Revo Uninstaller. This program can remove the registry edits from the drivers, giving you a completely clean install of the drivers. Reinstall the USB drivers: Latest version here, or a "tried 'n true version here". Both are worth trying. If you are using Windows 8, I strongly recommend you try Windows 7/XP. These drivers don’t usually work with Windows 8. (See here if you’re on Windows 8.) Otherwise, use the linked file to the Samsung USB drivers.

If you're still not having any luck, then follow these steps: (Credits to 4-2ndtwin)

1. Turn off both the computer and phone. Fully shut down.

2. Disconnect phone from computer: the USB cable from both the computer and phone.

3. Boot up the computer. Log in and let it settle.

4. Start up Odin and let it settle.

5. Put phone in download mode.

6. Connect phone to a USB port.

If that doesn't work, keep repeating those steps, with different USB ports on your PC/laptop. Change the USB cable you're using, multiple times (preferably use the cable that came with the phone). If all that doesn't work, start again at 'If Odin won't recognise the phone' on a different computer. Keep persevering :)

Now assuming you can get your phone into download mode, and is recognised by Odin:

Preliminary steps

Odin failing a flash usually isn’t a failure of the software itself. It’s usually to do with the way the flash is set up. Before we get on to the troubleshooting steps: you must always- i.e. every flash:

Run Odin as an administrator in Windows (only for Windows 7. This doesn’t apply for Windows XP). Yes, Odin is Windows only. If you use Linux/a Mac, you’ll need to use someone else’s Windows computer.

Ensure Kies is installed on your computer but you must kill all Kies running services in the Windows task manager. Most people have 4 running continuously. I personally only have 2, so don’t stress if you can’t find 4 to kill.

Make sure you're not using a USB hub of any description.

Remove your phone case, if you're using one. I've seen cases which make it not possible for the cable to correctly sit in the USB port.

If you haven’t done those steps on your previous Odin flash, it’s worth flashing again making sure you do those three things. Still didn’t work?

Troubleshooting steps

Things to do:

Change the USB cable you’re using. Preferably, use the original cable that came with the phone. If you’re already using the original cable, change to another, genuine, S2 cable. Try at least 3 different cables.

Remove your phone case, if you're using one. I've seen cases which make it not possible for the cable to correctly sit in the USB port.

Try different USB ports on your computer. You have to be using a mainboard (powered) port. Try as many of those as you have on your computer.

Use different versions of Odin: Attached at the bottom of this post is a zip file containing versions 1.3, 1.83, 1.85, 3.04 3.06, and 3.07. Try them all, but particularly 1.3, 1.85, 3.04 and 3.07. Make sure to extract the Odin files before using them.

Reinstall the Samsung USB drivers. If you are using Windows 8, I strongly recommend you try Windows 7/XP. These drivers don’t usually work with Windows 8. (See here if you’re on Windows 8.) Otherwise, use the linked file.

Turn off all antivirus/antimalware/antispyware/firewalls. I advise downloading all files you need before doing this step so you’re not without antivirus whilst downloading files. I’m not responsible if you do manage to get a computer virus during this time.

Check the rom/kernel you download, making sure it’s not a corrupted file. The best way to do this is to check the MD5 sum using md5summer. If you don’t have the MD5 sum, then you can use WinRar, 7Zip, or IZarc to test the file. If any tests (MD5 or the 7Zip test) fail, then you need to re-download the file. Test the new file before using it.

Run Windows update on the computer you’re using.

What now?

Ok, so if you’ve got to the bottom of the list, but you’re still having failed flashes:

Use a different computer. Now, run through the list again. Yes, the whole list. Try everything all over again on the new computer. Didn’t work? Try again on one more computer. Keep persevering, the feeling you’ll get when your S2 is back to life will be worth it :)

Last Resort

What if… Ok, so you genuinely can’t get anything to work. This really is a last resort. It’ll be either up to you to choose whether:

You research the flashing of .pit files. If you are going down that route and have an I9100, two good places to start are here and here.Note that your phone will be stuffed if it fails. Full stop. Motherboard replacement. Ask yourself “if Odin won’t flash a ROM without failing, why will it flash a .pit successfully?” Only click that link if you have tried the steps over and over and over again as stated.

You take your phone to a service centre.

Many thanks to keithross39 for proofreading & editing this guide, and re-hosting the 3-part firmware.

Also many thanks for It_ler for providing and hosting the 3-part firmware, after it was lost during the shutdown of hosting site hotfile.com.

Credits:

MistahBungle, on whose posts these troubleshooting steps are based.

keithross39, for his guide on replacing the USB port.

Intratech, for his guides on the basics of Odin flashing & stock ROM collection.

4-2ndtwin, for his troubleshooting steps if Odin won't recognise the phone.

SamHaLeKe, for the updated Samsung USB drivers.

ApriliaM3, for the USB driver hosting.

daerragh, for the Windows 8 drivers.

king_below_my_lord, for his guide on I9100 .pit file flashing.

metalgearhathaway, for his thread containing .pit files