GPS Doesn't Work

Question

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.

Answer 1

With the helpful assistance from couple of people from XDA Developers forum I was able to fix the GPS.

I have found a modem file that was supposed to fix it in this XDA thread, and did everything by the instructions there.

All I had to do is download a .zip file that contains two modem files (MK2 modem) in it, and flash them in order with Odin. After that I checked the GPS with GPS status app and it locked onto a satellite blazing fast.

I noticed couple of hours later that suddenly the cellular signal was really weak in area that should have full coverage. So I flashed this modem (BN4) and it fixed it (and the GPS also fine).