[Android Q&A, Help & Troubleshooting] hannibal.smith:
strange behaviour happened with my S4 (I9505). worked fluently for one year; in the meantime I flashed XENON HD, and still good for monthes. one day it was stucked in E (gprs edge). tried anything, forcing 3G (got no signal), recreate APN, but nothing. factory defaults no change. flashed back original samsung firmware, but still the same. with same SIM card in another phone 3g is fine.

tried different modem firmware versions, but still no luck.

I then tried to restore EFS, MODEMST1, MODEMST2, M9KEFS1, M9KEFS2, M9KEFS3 (I have full memory dump from the beginning) and with this LTE was back. but only for 10 minutes; than back to E. I've tried with any firmware, Xenon, Samsung original, behaviour is the same. works for a while then loses LTE forever. actually it's enough to restore M9KEFS* partitions and LTE is back.

from the logs I see this:

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08-09 17:06:47.773 1199 1199 D CellBroadcastReceiver: Intent: android.intent.action.SERVICE_STATE

08-09 17:06:55.656 573 594 D AlarmManagerService: Kernel timezone updated to -120 minutes west of GMT

08-09 17:06:55.668 1199 1199 D CellBroadcastReceiver: onReceive Intent { act=android.intent.action.SERVICE_STATE flg=0x10 cmp=com.android.cellbroadcastreceiver/.CellBroadcastReceiver (has extras) }

08-09 17:06:55.668 1199 1199 D CellBroadcastReceiver: Intent: android.intent.action.SERVICE_STATE

08-09 17:06:57.873 573 573 I GnssLocationProvider: WakeLock acquired by sendMessage(12, 0, null)

08-09 17:06:57.881 904 904 D MccTable: updateMccMncConfiguration mccmnc='null' fromServiceState=true

08-09 17:06:57.882 904 904 D MccTable: WIFI_COUNTRY_CODE set to

08-09 17:06:57.882 573 825 I WifiService: WifiService trying to set country code to with persist set to false

08-09 17:06:57.906 1199 1199 D CellBroadcastReceiver: onReceive Intent { act=android.intent.action.SERVICE_STATE flg=0x10 cmp=com.android.cellbroadcastreceiver/.CellBroadcastReceiver (has extras) }

08-09 17:06:57.906 1199 1199 D CellBroadcastReceiver: Intent: android.intent.action.SERVICE_STATE

08-09 17:06:57.906 1199 1199 D CellBroadcastReceiver: Service state changed! 1 Full: 1 0 voice roaming data roaming null null null null null null (manual) Unknown LTE CSS not supported -1 -1 RoamInd=-1 DefRoamInd=-1 EmergOnly=false IsDataRoamingFromRegistration=true IsUsingCarrierAggregation=false Current state=0

08-09 17:06:57.937 573 614 D GnssLocationProvider: GPS configuration:

08-09 17:06:57.937 573 614 D GnssLocationProvider: #Wed Aug 09 17:06:57 GMT+02:00 2017

08-09 17:06:57.937 573 614 D GnssLocationProvider: NTP_SERVER=time.gpsonextra.net

08-09 17:06:57.937 573 614 D GnssLocationProvider: A_GLONASS_POS_PROTOCOL_SELECT=0 \#Sensor R&D \: This will not be injected to MODEM

08-09 17:06:57.937 573 614 D GnssLocationProvider: INTERMEDIATE_POS=0

08-09 17:06:57.937 573 614 D GnssLocationProvider: USE_EMERGENCY_PDN_FOR_EMERGENCY_SUPL=1

08-09 17:06:57.937 573 614 D GnssLocationProvider: DEBUG_LEVEL=2

08-09 17:06:57.937 573 614 D GnssLocationProvider: SUPL_VER=0x10000

08-09 17:06:57.937 573 614 D GnssLocationProvider: NMEA_PROVIDER=1

08-09 17:06:57.937 573 614 D GnssLocationProvider: SGLTE_TARGET=0

08-09 17:06:57.937 573 614 D GnssLocationProvider: CAPABILITIES=0x37

08-09 17:06:57.937 573 614 D GnssLocationProvider: ERR_ESTIMATE=0

08-09 17:06:57.937 573 614 D GnssLocationProvider: XTRA_VERSION_CHECK=0

08-09 17:06:57.937 573 614 D GnssLocationProvider: SUPL_PORT=7275

08-09 17:06:57.937 573 614 D GnssLocationProvider: LPP_PROFILE=0 \# Sensor R&D \: This will not be injected to MODEM

08-09 17:06:57.937 573 614 D GnssLocationProvider: XTRA_SERVER_3=http\://xtrapath3.izatcloud.net/xtra2.bin

08-09 17:06:57.937 573 614 D GnssLocationProvider: SUPL_MODE=1

08-09 17:06:57.937 573 614 D GnssLocationProvider: XTRA_SERVER_2=http\://xtrapath2.izatcloud.net/xtra2.bin

08-09 17:06:57.937 573 614 D GnssLocationProvider: XTRA_SERVER_1=http\://xtrapath1.izatcloud.net/xtra2.bin

08-09 17:06:57.937 573 614 D GnssLocationProvider: SUPL_HOST=supl.google.com

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something modifies those partition/partitions, but can't imagine what.

any suggestion? can try anything, any hardware/software modifications.

david