Original post by: Tom Chai ,
The entire baseband subsystem is impossible to reprogram. It is possible to copy or repair the content on U601_RF, however it requires the U601_RF to be intact. The baseband main chip has its own boot chain so it may be possible to boot it and restore its own data into U601_RF. I haven't seen any successful repairs though. So my suggestion is try with a new U601_RF, if not working, replace U601_RF and U501_RF as a set, then use the factory tool to rewrite U4 to match new IMEI. Probably too difficult and too expensive so just replace the logic board or give up altogether.