SC668S-EM (Qualcomm Trinket) detects SIM but never registers on LTE network

IoT Modules Smart Module
1

Hello,

I’m troubleshooting a device based on the Quectel SC668S-EM (Qualcomm Trinket platform).

The SIM card is detected correctly, Android reads the operator information, and Qualcomm RIL services are running normally. However, the modem never registers on the cellular network.

AT command results:

AT+CPIN? → READY

AT+CREG? → 0,0

AT+CGREG? → 0,0

AT+CEREG? → 0,0

AT+CEER → No service available

Manual network selection with AT+COPS=1,2,“25001” also fails.

Additional observations:

  • Android detects the SIM card correctly.

  • No network operator is acquired.

  • Data connection never comes up.

  • modemst1 and modemst2 partitions exist and are not empty.

  • Qualcomm DIAG was enabled (sys.usb.config=diag,adb).

  • /dev/diag exists on the device.

  • DIAG does not enumerate on the PC.

At this point I’m trying to determine whether the issue is related to NV/EFS corruption, missing carrier configuration (MBN), RF hardware failure, or something else.

Has anyone seen a case where the modem detects the SIM correctly but CREG/CGREG/CEREG remain 0,0 permanently? Are there any recommended AT or QMI commands that can provide more detailed registration failure information?

Any suggestions would be greatly appreciated. Thanks.

2

Do you have our E-service account?

3

Unfortunately, I do not have

4

OK, we can chat here.

5

Ok, do you have any ideas on how I can solve my problem?

6

QCOM_V1.6.zip (883.6 KB)
Please use this tool to send the AT commands in the .ini file and send the result to us to check

7

AT+QMBNCFG=“autosel”
+QMBNCFG: “AutoSel”,1

OK
+QMBNCFG: “List”,0,1,1,“ROW_Commercial”,0x08010809
+QMBNCFG: “List”,1,0,0,“VoLTE-CU”,0x08011561
+QMBNCFG: “List”,2,0,0,“Lab_PTCRB_Test”,0x08010953
+QMBNCFG: “List”,3,0,0,“Telefonica_UK_Commercial”,0x08010C80
+QMBNCFG: “List”,4,0,0,“Telstra_Australia_Commercial”,0x08010F00
+QMBNCFG: “List”,5,0,0,“Optus_Australia_Commercial”,0x08014400
+QMBNCFG: “List”,6,0,0,“hVoLTE_OPNMKT_CT”,0x080113F1
+QMBNCFG: “List”,7,0,0,“Volte_OpenMkt-Commercial-CMCC”,0x08012010
+QMBNCFG: “List”,8,0,0,“Truemove_VoLTE_Commercial”,0x08012F00
+QMBNCFG: “List”,9,0,0,“AIS_Thailand_Commercial”,0x08012E00
+QMBNCFG: “List”,10,0,0,“CDMAless-Verizon”,0x08010127
+QMBNCFG: “List”,11,0,0,“Telus_Canada”,0x08014900
+QMBNCFG: “List”,12,0,0,“Commercial-TMO”,0x08010511
+QMBNCFG: “List”,13,0,0,“VoWiFi-Sprint”,0x08010220
+QMBNCFG: “List”,14,0,0,“Rogers_Canada”,0x08014800
+QMBNCFG: “List”,15,0,0,“Bell_Canada”,0x08014700
+QMBNCFG: “List”,16,0,0,“VoLTE-ATT”,0x08010336
+QMBNCFG: “List”,17,0,0,“FirstNet”,0x08015301
+QMBNCFG: “List”,18,0,0,“Commercial-SKT”,0x0801270A
+QMBNCFG: “List”,19,0,0,“Commercial-LGU”,0x08012608
+QMBNCFG: “List”,20,0,0,“Commercial-KT”,0x08012800
+QMBNCFG: “List”,21,0,0,“UK-VoLTE-Vodafone”,0x08010426
+QMBNCFG: “List”,22,0,0,“Spain-VoLTE-Vodafone”,0x08010485
+QMBNCFG: “List”,23,0,0,“TIM_Italy_Commercial”,0x08012B00
+QMBNCFG: “List”,24,0,0,“France-Commercial-Orange”,0x08010B21
+QMBNCFG: “List”,25,0,0,“Commercial-EE”,0x0801220B
+QMBNCFG: “List”,26,0,0,“Commercial-DT-VOLTE”,0x08011F1F
+QMBNCFG: “List”,27,0,0,“Commercial-SBM”,0x08011C0B
+QMBNCFG: “List”,28,0,0,“Commercial-Reliance”,0x08011B0C
+QMBNCFG: “List”,29,0,0,“Commercial-KDDI”,0x0801070B
+QMBNCFG: “List”,30,0,0,“Commercial-DCM”,0x08010D0E

OK
ATI+CSUB
Quectel
QCM6125
Revision: SC668SEMUAR04A02

SubEdition: V02

OK
AT+CVERSION
VERSION: SC668SEMUAR04A02
Dec 4 2023 11:49:22
Authors: QCT

OK
AT+QFSGVERSION?

SW: 20230602
RF: 20230530
Tag: SC668S-EM-R01-DS
Date: 20230602

OK
AT+EGMR=0,5
+EGMR: “P1C24CJ2B0006260P”

OK
AT+EGMR=0,7
+EGMR: “860979063630382”

OK
AT+EGMR=0,10
+EGMR: “860979063630390”

OK
AT+QCFG=“hotswap”
+QCFG: “HOTSWAP”,0,0

OK
AT$QCSIMAPP=?
$QCSIMAPP: 0,“SUB1”,“No Service”
$QCSIMAPP: 1,“SUB2”,“No Service”

OK
AT+QPRTPARA=4
Q4,1

OK
AT+CIMI
250019307418681

OK
AT+ICCID
ICCID: 89701018293074186816

OK
AT+CPIN?
+CPIN: READY

OK
AT+CFUN?
+CFUN: 1

OK
AT+CSQ
+CSQ: 20,99

OK
AT+COPS?
+COPS: 0

OK
AT+CGREG?
+CGREG: 0,2

OK
AT+CGDCONT?
+CGDCONT: 1,“IPV4V6”,“”,“0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0”,0,0,0,0
+CGDCONT: 2,“IPV4V6”,“ims”,“0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0”,0,0,0,0
+CGDCONT: 3,“IPV4V6”,“sos”,“0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0”,0,0,0,1
+CGDCONT: 4,“IPV4V6”,“xcap”,“0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0”,0,0,0,0
+CGDCONT: 5,“IP”,“internet.mts.ru”,“0.0.0.0”,0,0,0,0
+CGDCONT: 6,“IP”,“internet.mts.ru”,“0.0.0.0”,0,0,0,0

OK
AT+CGPADDR
+CGPADDR: 1,0.0.0.0,0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0
+CGPADDR: 2,0.0.0.0,0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0
+CGPADDR: 3,0.0.0.0,0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0
+CGPADDR: 4,0.0.0.0,0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0
+CGPADDR: 5,
+CGPADDR: 6,0.0.0.0

OK
AT$QCRSRP?
ERROR
AT+CREG?
+CREG: 0,2

OK
AT+CEREG?
+CEREG: 0,0

OK
AT+CGATT?
+CGATT: 0

OK
AT+CEER
+CEER: PDP establish timeout

OK
AT+COPS=?
+COPS: (1,“MTS RUS”,“MTS RUS”,“25001”,7),(1,“MTS RUS”,“MTS RUS”,“25001”,0),(1,“250 11”,“250 11”,“25011”,7),(1,“MegaFon RUS”,“MegaFon”,“25002”,2),(1,“MegaFon RUS”,“MegaFon”,“25002”,0),(1,“Tele2 RU”,“Tele2”,“25020”,2),(1,“Beeline”,“Beeline”,“25099”,7),(1,“MegaFon RUS”,“MegaFon”,“25002”,7),(1,“Tele2 RU”,“Tele2”,“25020”,7),(1,“Beeline”,“Beeline”,“25099”,0),(0,1,2,3,4),(0,1,2)

OK

8

we will check those commands

9

How about the antenna do you connect it?

And do you test with another SIM card?

10

The LTE antenna is connected properly to the MAIN LTE connector of the SC668S module.

The RF part seems to be working correctly because the module can detect all local operators:

  • MTS (25001)

  • MegaFon (25002)

  • Tele2 (25020)

  • Beeline (25099)

Signal strength is also good:

AT+CSQ
+CSQ: 20,99

I have tested with multiple SIM cards from different operators and the result is the same.

The module detects the SIM card correctly:

  • CPIN: READY

  • IMSI can be read successfully

  • ICCID can be read successfully

However, the module cannot register to the network:

  • CREG: 0,2

  • CGREG: 0,2

  • CEREG: 0,0

  • CGATT: 0

Could you please check whether the current MBN profile (ROW_Commercial) and firmware version SC668SEMUAR04A02 ?

11

let us confirm for the firmware.
By the way, canyou share the device IMEI1 and the picture for the device.

I want to confirm whether you can download our officail firmware

12

photo_2026-06-04_08-29-50
photo_2026-06-04_08-29-50960×1280 325 KB

IMEI1: 860979063630382

The module information is:

Model: SC668S-EM
Firmware: SC668SEMUAR04A02
Hardware Tag: SC668S-EM-R01-DS

Could you please confirm whether this module is eligible for official Quectel firmware upgrade and whether a newer firmware version is available?

13

It seems the device is get from the third party, we can release you the officail firmware,

but with the officail firmware only the default function of the module can work,

for the customize function like the LCD, sensor or camera and so on they will not work.

14

Thank you for the clarification.

I understand that the official firmware may not support the customized functions of the head unit (LCD, touchscreen, camera, CAN bus, audio and other peripherals).

At this stage I would prefer not to replace the complete Android firmware.

Could you please advise whether there is:

  • a modem/baseband firmware update only,

  • an MBN package update,

  • or a modem configuration update

that can be applied without replacing the entire system image?

The LTE modem can detect operators correctly and signal strength is good, but it cannot register to the network.

I would like to keep the existing customized Android system and only update the modem-related components if possible.

15

Yes we can update the modem individually,
let I will send the file