[Optimus One, P500 Android Development] Gremaldin:
Disclaimer: I will not be responsible for anything that happens to your phone after following this post. You are doing this because you choose to and you alone are responsible for anything that may happen. Use at your own risk.

NOTE: This should work for any screen you are stuck at. I'm just mentioning the screens I have come across.

If your phone is stuck at the LG/Android boot screen or emergency mode or a black screen saying

fastboot mode started
udc_start()

then your phone isn't bricked, you dont need to panic. Your phone can be fixed right at home by following these steps.

After doing some research, I found that

fastboot mode started
udc_start()

is displayed when we do something like install custom recovery and failed. There may or may not be additional lines of text, but the procedure is the same for all such cases where the starting 2 lines are the above.

If you can boot into recovery mode (holding the home button, the lower volume button and the power button together after turning off the phone), and if you ave previously backed up your stock ROM, then you can simply flash that through recovery. Remember that the touch screen doesn't work in recovery mode, you will have to use volume up and down buttons to navigate and the menu button to select an option.

The method below works even if you cant boot into recovery.

1. Download KDZ Updater and LG united mobile drivers from here.

2. Extract the rar file and install LG United mobile drivers.

3. Disable all LGE modems under modems from windows device manager.

4. Charge your phone since we cant really tell how much juice is left in the battery even though the screen is on.

5. Download the stock firmware (also known as rom) from Lg’s firmware repository. You can download the firmware and firmware version suiting your region from the links I have provided below. But many of these links may not work, so to download the stock 2.2.2 ROM build V10D_00 for India, click here. If you choose to download this stock ROM, then ignore Methods 1 & 2 given below. If however you want to download a ROM for a different country and version, then follow Method 1 or 2.

Method 1:

The following link will list all the country codes for LG optimus p 500.

http://csmg.lgmobile.com:9002/csmg/b2c/client/ezlooks_model_list.jsp?model=LGP500

Press ctrl + f on the keyboard to bring up the browser search tool and type the name of your country.

Copy your country’s code. For example for india its AINDBK. Now paste it in the url below where it is marked XXXXXX.

http://csmg.lgmobile.com:9002/swdata/WEBSW/LGP500/XXXXX/V10b_00/V10B_00.kdz

Your link would look something like this after pasting the code

http://csmg.lgmobile.com:9002/swdata/WEBSW/LGP500/AINDBK/V10b_00/V10B_00.kdz

Replace the V10b_00/V10B_00.kdz with the version number you want. For example if i want to install version 10C then i would change the letters from c to b like this V10c_00/V10C00.

Now copy and paste the link in the addressbar of your browser and press enter key. Download should start.

This method may not work for all countries.

Method 2:

If the above method didn't work (it didn't for me), then here’s a list of the latest unbranded firmware as of 9/03/2011 4:15 EST

Just click on the links below to start the DOWNLOAD

6. Install msxml (from the KDZ Updater folder) on your windows pc by double clicking it.

7. a. If your phone is stuck at the Android screen or LG screen or Emergency screen, connect your phone to your PC via USB.

b. If your phone is stuck at fastboot mode started udc_start() screen, then remove the battery and reinsert it. Now press the back key and volume up button and simultaneously connect your phone to your PC. You will get a greenish yellow screen saying Emergency mode.

8. Run KDZ_FW_UPD.exe with administrator privilages (right click, run as administrator in win7).

9. In the software window, select Type as 3GQCT

Select PhoneMode as "DIAG" if your phone is not in emergency mode (i.e., if your phone is in LG/Android screen). If you are in emergency mode, select "Emergency".

In the place where you have to give path for KDZ file, select the Firmware a.k.a ROM you have downloaded using the link you made for your country specific firmware.

10. Press Launch software update and wait for about 10 or 15 minutes. The screen will then say “Emergency mode”. Just wait and let it reboot. Do not disconnect your phone till it is shown "finished".

11. Now switch on your phone. Finished!

[OPTIONAL] Hit the thanks button!

Note: If kdz is unable to see your phone, then try running kdz in compatibility mode for XP, restarting your phone, shaking your phone (I know it sounds crazy but it works sometimes!), restarting your computer, try and try again till it works.

NOTE: If KDZ stops working and phone gets stuck in recovery mode and you have to remove the battery just to turn off the phone, and you cant get into recovery mode or emergency mode, but you're stuck at a black screen, remove the battery and connect the phone via USB to a computer which has LG United mobile drivers installed. Disable all LGE modems under modems from windows device manager.

Unplug the usb cord from your PC and plug it in again. You still shouldn't have a battery in your phone, yet by plugging it in the "Emergency mode" should start automatically. Open up KDZ, select Type "3GQCT" and PhoneMode "EMERGENCY". Select a KDZ file and flash it.

NOTE: If your phone doesn't even turn on, the try holding back + vol up + power and simultaneously connect to a computer which has LG United mobile drivers intstalled via USB. Then you should reach emergency mode. Then just follow the steps mentioned above.

I know that almost all of the above info is already available in different threads, I just wanted to bring all that info together in 1 easy to find post, because when I bricked my phone I had to refer multiple threads and posts (and even some other sites) to make sure of what I was doing and get things right.