Flashing Modem Firmware
To force flash the phone modem in WebOS you need to use PmModemUpdater.
Why you might need to Flash Modem Firmware
Flashing modem firmware comes in handy if your phone is stuck in phone offline mode and will not connect to a cell signal due to modem firmware corruption. Generally caused by phone being powered down in the middle of "Full Erase" or WebOS Doctor. The phone modem firmware version becomes unknown preventing WebOS Doctor to automatically flash it during operation. To check if your phone modem is unknown type ##radio# (##72346#) in phone app and it should give you your modem firmware version otherwise say unknown.
Your modem firmware might be unknown if you are receiving the following error on a phone that is stuck in First Use without activation.
The error will loop First Use card with this message:
Your phone is experiencing an error that cannot be resolved.
Visit www.palm.com for help."
What You Need First
Before you Force Flash your modem's firmware because your it is stuck offline, you should try turning airplane mode on and off, reseting the phone, running WebOS Doctor, and any other safer/easier idea you may have. As flashing modem firmware can potentially harm your modem. As this is the message that appears when you run the PmModemUpdater command Warning!
Warning! Please make sure you have a healthy battery or using a power supply before you do your update Warning! You can potentially trashed your modem firmware if system lost the power in the middle of updating firmware Warning! To Stop it now, ctrl+c
How To Do It
<Note these steps are written for an original Sprint Palm Pre you need to adapt for your device>
Step 1 - First you need to download the WebOS Doctor  version that you need. DO NOT USE ANY OTHER DOCTOR THAT IS NOT DESIGNED FOR YOUR PHONE.
Step 2 -
a. You need to extract the jar file using your favorite archiver program WinRar works fine for windows usres.
b. Resource directory includes the file webOS.tar you will need to extract this as well.
c. Within webOS.tar you will find two other .tar files you need to transfer castlecdmafw.tar (Alternativly castleumtsfw.tar for GSM) to your phone's media directory root (connect phone as USB Drive and transfer it to main area not in a folder)