I have SGH-M919 (SGS4 T-Mobile variant). First, it had stock ROM, stock firmware, and it was SIM locked to T-Mobile, so I unlocked it with SRS server service (I live outside the US, so labs in my area didn't have the tools to unlock it, since it's only a US variant. Also, other methods of unlocking did not work for me, unfortunately).
In the unlocking process I had to flash custom modem file with Odin (it was required for SRS to work). After the successful unlock, I flashed CWM and CM11, rooted the device with Kingo ROOT and everything worked fine except the GPS. It didn't work: no GPS satellites were found.
How can I solve this issue? Thanks.
I have already tried:
Reverting to stock firmware (by flash. Kies doesn't work). No only that it didn't fix it, the WiFi broke and couldn't be turned on. I has to recover everything with a recovery file I have made with CWM.
Installing stock ROM via the recovery. The GPS worked(ish), but was very slow. I then restored my CM setup with nandroid restore (again, via the recovery), and the GPS didn't work again.
While using the stock ROM, I tried to get to LbsTestMode in order to fix the GPS, as explained here, but I couldn't reach it - it just doesn't exist in Android 4.4.2 apparently.