Originally Posted by stalin.sk2
You can't unlock bootloader if your device service info says "bootloader unlock allowed:no"
Sent from my C2004 using xda app-developers app
I was reading on the Sony forums a while back that you can. It was in the support for the Z forum so I don't know if it will work on the M. If the phone is locked to a network (the most common form of bootloader unlock:no) and you unlock it and THEN flash an unbranded firmware the bootloader status will change from no to yes. That post was made by a Sony support person too, but as I said, I have no idea if it would work on the M.
My Phone: Sony Xperia M C1905 | ROM: Modified Stock | Base Firmware/Build Number: 15.4.A.0.23 | Android Version: 4.3 | Kernel: Stock (Permanently Locked Bootloader) | Network: GiffGaff
My Tablet: Google Nexus 7 (2012) | ROM: CM11 | Base Firmware/Build Number: 11-20140527-NIGHTLY-grouper | Android Version: 4.4.4 | Kernel: CM11 | Network: N/A