Device Information
- Model: TRB246
- Firmware: TRB2M_R_00.07.15.4 (Build: d0faa4d6d30, 2025-07-10 11:55:42)
- Kernel: 5.15.180
- BusyBox: v1.34.1
- MAC Address: -
Cellular Modem Details
- Modem: Quectel EC25-EUX
- Firmware: EC25EUXGAR08A15M1G_20.200.20.200
- USB ID: 2c7c:0125
- USB Path: 1-1.4
- Serial Devices: /dev/ttyUSB0-4 (all present)
SIM Card Information
- IMSI: - (Vodafone UK)
- CCID: -
- SIM Status: +CPIN: READY
- SIM Slot: 1
We have 3 identical TRB246 modems deployed in the same location:
- Same antennas (identical hardware setup)
- Same SIM cards (Vodafone UK)
- Same configuration (APN “internet”, no authentication)
- Same coverage area (side by side installation)
Status:
TRB246 #1: Working normally with internet connectivity- TRB246 #2: Working normally with internet connectivity
TRB246 #3: FAILED after reboot - cannot establish cellular connection
Problem Description
TRB246 #3 was working normally with internet connectivity, then suddenly stopped working after a reboot. The other two identical units continue to work perfectly in the same location, confirming this is not a network, coverage, or configuration issue.
Current Status of the TRB246 not working
- Network Registration: +CREG: 2,0 (Not registered)
- Signal Strength: +CSQ: 99,99 (No signal/unknown)
- Network Search: +QENG: “servingcell”,“SEARCH” (Continuously searching)
- Network Scan: AT+COPS=? returns ERROR
- SIM Detection: Working properly
- Modem Communication: AT commands respond correctly
APN Settings Tested:
- Original: wap.vodafone.co.uk with username/password wap/wap
- Updated: internet (no authentication) - as recommended by SIM provider
Current UCI Configuration:
network.mob1s1a1.proto=‘wwan’
network.mob1s1a1.apn=‘internet’
network.mob1s1a1.auto_apn=‘0’
network.mob1s1a1.pdptype=‘ipv4’
network.mob1s1a1.username=‘’
network.mob1s1a1.password=‘’
network.mob1s1a1.auth=‘’
Current Modem PDP:
+CGDCONT: 1,“IP”,“internet”,“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
Debug Tests Performed
Signal and Registration Tests:
- AT+CSQ → +CSQ: 99,99 (No signal)
- AT+CREG? → +CREG: 2,0 (Not registered)
- AT+CGREG? → +CGREG: 2,0 (Not registered)
- AT+COPS=? → ERROR (Cannot scan networks)
- AT+COPS? → Tested
- AT+COPS=0 → OK (but no effect)
Network Technology Tests:
- AT+QCFG=“nwscanmode” → +QCFG: “nwscanmode”,0 (Auto mode)
- Attempted GSM-only mode: AT+QCFG=“nwscanmode”,1
- Attempted LTE-only mode: AT+QCFG=“nwscanmode”,3
- Band configuration: +QCFG: “band”,0x93,0x1a0080800c5,0x0
Modem Reset Attempts:
- AT+CFUN=1,1 → OK (Functional reset performed)
- AT&F → Factory reset attempted
- USB interface resets via sysfs unbind/bind
- Multiple interface restarts: ifdown/ifup mob1s1a1
- Network service restart: /etc/init.d/network restart
Hardware Tests:
- lsusb → Modem detected as ID 2c7c:0125
- USB serial devices → All 5 ttyUSB devices present
- ATI → Modem responds with model information
- AT+CIMI → SIM IMSI readable
- AT+CCID → SIM card ID readable
Observations
- Hardware appears functional - All AT commands respond, SIM detected
- RF scanning completely broken - AT+COPS=? returns ERROR
- Continuous search mode - +QENG: “servingcell”,“SEARCH”
- Physical connectivity confirmed - Antenna connected, strong coverage area
- Problem started after reboot - Was working before system restart
The cellular modem’s RF scanning hardware appears to be in a corrupted state after the reboot. Despite proper antenna connection and being in a strong coverage area, the modem cannot detect any cellular networks (AT+COPS=? ERROR).
Can you please help? I have a CLI working connection with the faulty modem.
I appreciate your help and suggestions,
Alberto