nRF9151 stuck in disconnected, unable to reconnect to LTE-M

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

Menon — Tue, 15 Jul 2025 10:10:54 GMT

Hello,

[quote user="teba99"]We will continue to test the connectivity robustness and report back[/quote]

Please let me know if something important comes up.

Kind Regards,

Abhijith

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

teba99 — Mon, 14 Jul 2025 21:39:02 GMT

Hi Abhijith,

Thanks for the detailed investigation. That makes sense. As explained, one way we triggered this issue was to briefly deactivate, then re-activate the SIM. We're not sure why that means the device cannot attempt EPS connections again to that PLMN ... this seems to be a valid case, but if that's the standard then we'll go with it . ;-)

However, as described above, we also seem to see this problem if the device looses the connection due to poor signal/coverage. In that case, too, the device is never able to reconnect. However, that case is much harder to reproduce, so I can't provide a modem trace at this time.

Anyway, it's good to know that for "EMM cause 7" this is the expected behavior and not a bug in the nRF network stack. As described we work around it by toggling the network interface.

We will continue to test the connectivity robustness and report back.

Thanks,
-- Terrence

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

Menon — Mon, 14 Jul 2025 19:13:47 GMT

Hello Terrence,

Sorry for getting back to you a bit late.

We reviewed the modem trace and noticed the following:

An Onomondo MVNO SIM was used in the DTAG network.
Attach and a few data transfers worked initially, but eventually the network detached the device.
The Detach Request message included EMM cause 7: EPS services not allowed, which according to 3GPP means the device cannot attempt EPS connections again in that PLMN.
Recovery is only possible via a restart or by issuing CFUN=0 followed by CFUN=1.

The Detach Request included:

NAS EPS Mobility Management Message Type: Detach request (0x45)
Detach Type: Re-attach not required (2)
EMM Cause: EPS services not allowed (7)

So you need to ask Onomondo/DTAG why this is happening. Onomondo provides Wireshark logs from their core network, so the cause should be visible there as well. Once you figure out why the Onomondo SIM card is being rejected by DTAG, you won’t need any workarounds.

Kind Regards,

Abhijith

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

Menon — Wed, 02 Jul 2025 09:07:36 GMT

Hello,

Thanks for the update, it's good to hear that you've found a workaround. We are still investigating this on our end.

As it's the summer vacation period here, please expect some delay from our side. Apologies for the inconvenience.

Kind regards,
Abhijith

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

teba99 — Wed, 02 Jul 2025 07:14:50 GMT

Hi Menon ,

After some experimentation we were able to apply a workaround that seems to address the problem.

If connection reestablishment continues to fail and the network is not available for some time (e.g. 5 minutes) then instead of continuing to wait for connection reestablishment we now added code to toggle the network interfaces:

conn_mgr_all_if_disconnect(true);

conn_mgr_all_if_connect(true);

After that, the connection establishment succeeds within about 15 seconds without any further action.

Best,
Terrence

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

teba99 — Mon, 30 Jun 2025 21:09:16 GMT

Hi,

Sorry, I now attached the trace to my previous post.

Thanks,

Terrence

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

Menon — Mon, 30 Jun 2025 13:31:04 GMT

Hello Terrence,

Thanks for the update. I’ve reported this issue internally, but to investigate further, we need a modem trace. I didn’t see one attached in your last response.

If you missed attaching it, please upload the trace using the Insert tab.

Kind regards,
Abhijith

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

teba99 — Fri, 27 Jun 2025 05:29:22 GMT

Hi Menon ,

I was able to do some more testing and create modem traces.

I reproduced the problem with the nRF SDK 2.9.0 Modem Shell application on a nRF9161-DK. This means the problem is not related to our hardware or application, but must be somewhere in the nRF software stack.

I used the Modem Shell unmodified, just built it with CONFIG_MOSH_CLOUD_MQTT=y and the nrf91-modem-trace-uart snippet.

Here is the trace in the serial window. At ">>>" you see my comments interleaved.

You can see that after the loss of the connection (poor signal or brief deactivation of SIM) the modem is in auto-connect mode and sees networks, but doesn't try to reconnect. It just 'sits there'. I have experience with other modems (e.g. Quectel) and in such cases the modem would automatically try to reconnect.

When I 'kick' the nRF9161 (cfun=4, then cfun=1) it immediately reestablishes the connection.

To me this indicates that after connection loss the modem gets stuck in some state where it fails to try and auto-connect, and that state is only cleared with a modem soft reset.

I've very similar reports from other developers: https://community.circuitdojo.com/d/224-reconnecting-lte-after-disconnect.

>>> Reboot:

Booting TF-M v2.1.1-ncs3

[Sec Thread] Secure image initializing!

TF-M isolation level is: 0x00000001

TF-M Float ABI: Hard

Lazy stacking enabled

*** Booting nRF Connect SDK v2.9.0-7787b2649840 ***

*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***

Reset reason: PIN reset

mosh:~$

MOSH version: v2.9.0-7787b2649840

MOSH build id: custom

MOSH build variant: dev

HW version: nRF9161 LACA ADA

Modem FW version: mfw_nrf91x1_2.0.0

Modem FW UUID: c234531b-9f14-4135-9092-f4e52d37fb23

> at AT+CGMR

at AT+CGMR

mfw_nrf91x1_2.0.0

OK

mosh:~$ > at AT+CFUN=1

at AT+CFUN=1

OK

mosh:~$ > at AT%XCONNSTAT=1

at AT%XCONNSTAT=1

OK

mosh:~$ > at AT%XCONNSTAT?

at AT%XCONNSTAT?

%XCONNSTAT: 0,0,0,0,0,0

OK

mosh:~$ > at AT+CMEE=1

at AT+CMEE=1

OK

mosh:~$ > at AT%XSIM=1

at AT%XSIM=1

OK

mosh:~$ > at AT+CEREG=5

at AT+CEREG=5

OK

mosh:~$ > at AT%MDMEV=1

at AT%MDMEV=1

OK

mosh:~$ > at AT%CESQ=1

at AT%CESQ=1

OK

mosh:~$ > at AT+CGSN=1

at AT+CGSN=1

+CGSN: "352696950002997"

OK

mosh:~$ > at AT+CGMM

at AT+CGMM

nRF9161-LACA

OK

mosh:~$ > at AT+CEMODE?

at AT+CEMODE?

+CEMODE: 2

OK

mosh:~$ > at AT+CMEE?

at AT+CMEE?

+CMEE: 1

OK

mosh:~$ > at AT+CNEC?

at AT+CNEC?

+CNEC: 16

OK

mosh:~$ > at AT+CGEREP?

at AT+CGEREP?

+CGEREP: 1,0

OK

mosh:~$ at A> at AT+CIND=1,1,1

T+CIND=1,1,1

OK

mosh:~$ > at AT+COPS=3,2

at AT+COPS=3,2

OK

mosh:~$ > at AT+CGDCONT?

at AT+CGDCONT?

OK

mosh:~$ > at AT+CGACT?

at AT+CGACT?

OK

mosh:~$ > at AT+CESQ

at AT+CESQ

+CESQ: 99,99,255,255,255,255

OK

mosh:~$ > at AT%XSIM?

at AT%XSIM?

%XSIM: 0

OK

mosh:~$ > at AT+CPIN?

at AT+CPIN?

+CME ERROR: 13

mosh:~$ > at AT+CIMI

at AT+CIMI

+CME ERROR: 0

mosh:~$ > at AT+CNEC=24

at AT+CNEC=24

OK

mosh:~$ > at AT+CEER

at AT+CEER

OK

mosh:~$ > at AT+CGEREP=1

at AT+CGEREP=1

OK

mosh:~$ > at AT%XPOFWARN=1,30

at AT%XPOFWARN=1,30

OK

mosh:~$ > at AT%XVBATLVL=1

at AT%XVBATLVL=1

OK

mosh:~$ > at AT+CGMI

at AT+CGMI

Nordic Semiconductor ASA

OK

mosh:~$ > at AT+CGMR

at AT+CGMR

mfw_nrf91x1_2.0.0

OK

mosh:~$ > at AT+CGSN

at AT+CGSN

352696950002997

OK

mosh:~$ > at AT%XMODEMUUID

at AT%XMODEMUUID

%XMODEMUUID: c234531b-9f14-4135-9092-f4e52d37fb23

OK

mosh:~$ > at AT%XDATAPRFL?

at AT%XDATAPRFL?

%XDATAPRFL: 2

OK

mosh:~$ > at AT+CEREG?

at AT+CEREG?

+CEREG: 5,0

OK

mosh:~$ > at AT+CFUN?

at AT+CFUN?

+CFUN: 1

OK

mosh:~$ > at AT%CESQ=1

at AT%CESQ=1

OK

mosh:~$ > at AT+CSCON=1

at AT+CSCON=1

OK

mosh:~$ > at AT+CSCON?

at AT+CSCON?

+CSCON: 1,0

OK

mosh:~$ > at AT+CPAS

at AT+CPAS

+CPAS: 0

OK

mosh:~$ > at AT+CEDRXRDP

at AT+CEDRXRDP

+CEDRXRDP: 0

OK

mosh:~$ > at AT%XTIME=1

at AT%XTIME=1

OK

mosh:~$ > at AT%CONEVAL

at AT%CONEVAL

%CONEVAL: 1

OK

mosh:~$ > at AT%XCBAND=?

at AT%XCBAND=?

%XCBAND: (1,2,3,4,5,8,12,13,18,19,20,25,26,28,66,85)

OK

mosh:~$ > at AT%XCBAND

at AT%XCBAND

%XCBAND: 0

OK

mosh:~$ > at AT%HWVERSION

at AT%HWVERSION

%HWVERSION: nRF9161 LACA ADA

OK

mosh:~$ > at AT%XMODEMTRACE=1,2

at AT%XMODEMTRACE=1,2

OK

mosh:~$ > at AT%XSYSTEMMODE?

at AT%XSYSTEMMODE?

%XSYSTEMMODE: 1,0,0,0

OK

mosh:~$ > at AT%XICCID

at AT%XICCID

%XICCID: 89457300000010597907

OK

mosh:~$ > at AT%XEMPR?

at AT%XEMPR?

%XEMPR:

OK

mosh:~$ at AT+CGDC> at AT+CGDCONT?

ONT?

OK

mosh:~$ > at AT+COPS?

at AT+COPS?

+COPS: 0

OK

mosh:~$ > at AT%XMONITOR

at AT%XMONITOR

%XMONITOR: 0

OK

mosh:~$ > at AT+CPINR="SIM PIN"

at AT+CPINR="SIM PIN"

+CPINR: "SIM PIN",3

OK

mosh:~$ > at AT+CPINR="SIM PIN2"

at AT+CPINR="SIM PIN2"

+CPINR: "SIM PIN2",3

OK

mosh:~$ > at AT+CPINR="SIM PUK"

at AT+CPINR="SIM PUK"

+CPINR: "SIM PUK",10

OK

mosh:~$ > at AT+CPINR="SIM PUK2"

at AT+CPINR="SIM PUK2"

+CPINR: "SIM PUK2",10

OK

mosh:~$ > at AT%XSIM?

at AT%XSIM?

%XSIM: 1

OK

Network registration status: searching

Currently active system mode: LTE-M

LTE cell changed: ID: 45508877, Tracking area: 26552

RRC mode: Connected

PDN event: PDP context 0 activated

PDN event: PDP context 0, PDN type IPv4 only allowed

Modem domain event: Search done

Network registration status: Connected - roaming

PSM parameter update: TAU: 3240, Active time: -1 seconds

Modem config for system mode: LTE-M

Modem config for LTE preference: No preference, automatically selected by the modem

Currently active system mode: LTE-M

Battery voltage: 5042 mV

Modem temperature: 27 C

Device ID: nrf-352696950002997

Operator full name: ""

Operator short name: ""

Operator PLMN: "26201"

Current cell id: 45508877 (0x02B6690D)

Current phy cell id: 337

Current band: 3

Current TAC: 26552 (0x67B8)

Current rsrp: 37: -104dBm

Current snr: 29: 5dB

Mobile network time and date: 25/06/27,04:58:30+08

PDP context info 1:

CID: 0

PDN ID: 0

PDP context active: yes

PDP type: IP

APN: onomondo

IPv4 MTU: 1360

IPv4 address: 100.76.21.49

IPv6 address: ::

IPv4 DNS address: 172.30.8.5, 172.30.8.6

IPv6 DNS address: ::, ::

RRC mode: Idle

>>> connection established, everything OK. Establish MQTT cloud connection:

mosh:~$ > cloud connect

cloud connect

Endpoint: mqtt.nrfcloud.com

Connecting to nRF Cloud...

nRF Cloud event: NRF_CLOUD_EVT_TRANSPORT_CONNECTING

RRC mode: Connected

[00:00:45.708,557] <inf> nrf_cloud_info: Device ID: nrf-352696950002997

[00:00:45.717,956] <inf> nrf_cloud_info: IMEI: 352696950002997

[00:00:45.810,791] <inf> nrf_cloud_info: UUID: 50363953-3234-40cb-80ae-1e21b10ad7e4

[00:00:45.816,925] <inf> nrf_cloud_info: Modem FW: mfw_nrf91x1_2.0.0

[00:00:45.816,955] <inf> nrf_cloud_info: Protocol: MQTT

[00:00:45.816,986] <inf> nrf_cloud_info: Download protocol: HTTPS

[00:00:45.817,016] <inf> nrf_cloud_info: Sec tag: 16842753

[00:00:45.817,047] <inf> nrf_cloud_info: Host name: mqtt.nrfcloud.com

nRF Cloud event: NRF_CLOUD_EVT_TRANSPORT_CONNECTED

nRF Cloud event: NRF_CLOUD_EVT_RX_DATA_SHADOW

nRF Cloud event: NRF_CLOUD_EVT_USER_ASSOCIATED

[00:00:49.732,299] <inf> nrf_cloud_log: Changing cloud log level from:1 to:3

[00:00:49.732,330] <inf> nrf_cloud_log: Changing cloud logging enabled to:1

nRF Cloud event: NRF_CLOUD_EVT_READY

Connection to nRF Cloud established

[00:00:51.133,270] <inf> nrf_cloud_info: Team ID: be46c77d-xxx

RRC mode: Idle

>>> Attached network info

mosh:~$ > at at+cops?

at at+cops?

+COPS: 0,2,"26201",7

OK

mosh:~$ > at at+cereg?

at at+cereg?

+CEREG: 5,5,"67B8","02B6690D",7,,,"11100000","11100000"

OK

RRC mode: Connected

>>> Now: Loss of connectivity:

nRF Cloud event: NRF_CLOUD_EVT_TRANSPORT_DISCONNECTED, status: 3

Network registration status: not registered

Connection to nRF Cloud disconnected

PDN event: PDP context 0 network detach

Reconnecting in 10 seconds...

RRC mode: Idle

[00:01:53.207,977] <wrn> lte_lc: Registration rejected, EMM cause: 7, Cell ID: 45508877, Tracking area: 26552, LTE mode: 7

Connecting to nRF Cloud...

nRF Cloud event: NRF_CLOUD_EVT_TRANSPORT_CONNECTING

nRF Cloud event: NRF_CLOUD_EVT_TRANSPORT_CONNECT_ERROR, status: -9

Connecting to nRF Cloud failed

[00:02:03.257,019] <err> nrf_cloud_transport: Could not connect to nRF Cloud MQTT Broker mqtt.nrfcloud.com, port: 45858. err: -111

>>> Modem sees networks, is in automatic mode, but does not try to reconnect

mosh:~$ > at at+cereg?

at at+cereg?

+CEREG: 5,0

OK

mosh:~$ > at at+cops?

at at+cops?

+COPS: 0

OK

mosh:~$ at at+cops=?

> at at+cops=?

+COPS: (1,"","","26203",7),(1,"","","26201",7),(1,"","","26202",7)

OK

Currently active system mode: None

LTE cell changed: ID: -1, Tracking area: -1

mosh:~$ at AT+CGDC> at AT+CGDCONT?

ONT?

OK

>>> manually force offline mode, then back to normal mode

mosh:~$ > at at+cfun=4

at at+cfun=4

OK

mosh:~$ > at at+cfun=1

at at+cfun=1

OK

>>> modem reestablishes connection without further input or actions

Network registration status: searching

Currently active system mode: LTE-M

LTE cell changed: ID: 45508865, Tracking area: 26552

RRC mode: Connected

PDN event: PDP context 0 activated

PDN event: PDP context 0, PDN type IPv4 only allowed

Modem domain event: Search done

Network registration status: Connected - roaming

Modem config for system mode: LTE-M

Modem config for LTE preference: No preference, automatically selected by the modem

Currently active system mode: LTE-M

Battery voltage: 5031 mV

Modem temperature: 28 C

Device ID: nrf-352696950002997

Operator full name: ""

Operator short name: ""

Operator PLMN: "26201"

Current cell id: 45508865 (0x02B66901)

Current phy cell id: 379

Current band: 20

Current TAC: 26552 (0x67B8)

Current rsrp: 46: -95dBm

Current snr: 30: 6dB

Mobile network time and date: 25/06/27,05:02:49+08

PDP context info 1:

CID: 0

PDN ID: 0

PDP context active: yes

PDP type: IP

APN: onomondo

IPv4 MTU: 1360

IPv4 address: 100.76.21.49

IPv6 address: ::

IPv4 DNS address: 172.30.8.5, 172.30.8.6

IPv6 DNS address: ::, ::

LTE cell changed: ID: 30601474 (0x01D2F102), PCI 164, Tracking area: 26552 (0x67B8), Band: 3, RSRP: 36 (-105dBm), SNR: 29 (5dB)

>>> Reestablish MQTT cloud connection

mosh:~$ > cloud connect

cloud connect

Endpoint: mqtt.nrfcloud.com

Connecting to nRF Cloud...

nRF Cloud event: NRF_CLOUD_EVT_TRANSPORT_CONNECTING

nRF Cloud event: NRF_CLOUD_EVT_TRANSPORT_CONNECTED

nRF Cloud event: NRF_CLOUD_EVT_RX_DATA_SHADOW

nRF Cloud event: NRF_CLOUD_EVT_USER_ASSOCIATED

nRF Cloud event: NRF_CLOUD_EVT_READY

Connection to nRF Cloud established

[00:05:04.917,236] <inf> nrf_cloud_info: Team ID: be46c77d-e0a8-4ee0-92cc-85525808fc1b

RRC mode: Idle

LTE cell changed: ID: 45508877 (0x02B6690D), PCI 337, Tracking area: 26552 (0x67B8), Band: 3, RSRP: 38 (-103dBm), SNR: 31 (7dB)

mosh:~$

devzone.nordicsemi.com/.../trace_2D00_2025_2D00_06_2D00_27T04_2D00_58_2D00_14.712Z.mtrace

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

Menon — Tue, 24 Jun 2025 11:21:47 GMT

Hello Akshay,

I kindly recommend creating a separate ticket for your issue, as each case is handled independently. Once you've created the new ticket, please share the relevant details there, similar to what I've requested in this conversation.

Kind regards,
Abhijith

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

Akshay — Fri, 20 Jun 2025 07:26:58 GMT

I'm also facing the exact same issue, have you managed to get any work around for this?

best regards,

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

teba99 — Tue, 10 Jun 2025 20:55:25 GMT

Hi Menon ,

In the meantime, I am also seeing inability to reconnect even in the case of a simple connection loss due to poor signal.

The device starts up and connects right away without problems. Later, I add 30 dB attenuation to the antenna path to simulate a poor connection. The device disconnects after a few seconds, as expected. Then I remove the attenuation and I would expect the device to reconnect because the signal is now good again. However, the device is unable to reconnect. The logs I get:

[00:00:47.145,690] <inf> app_cloud_connection: Disconnected from nRF Cloud

[00:00:47.145,690] <inf> app_cloud_connection: Retrying in 30 seconds...

[00:01:17.145,812] <inf> app_cloud_connection: Waiting for network ready...

[00:01:17.253,692] <err> modem_info_params: Link data not obtained: 5 -5

[00:01:17.253,723] <wrn> app_message_sender: Could not obtain information from modem, error: -5

[00:01:17.254,486] <inf> app_cloud_connection: Could not send a device message - no connection

[00:01:25.806,854] <wrn> lte_lc: Registration rejected, EMM cause: 9, Cell ID: 23438850, Tracking area: 59672, LTE mode: 7

This continues for a long time (many minutes) and the device only connects again after a reboot. Note that I made no changes on the network side and the SIM is always active and the network should be accessible.

Again, this looks like the connectivity stack get stuck in some state after it looses the connection the first time and then is unable to reconnect by itself.

I will work on getting modem traces.

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

teba99 — Tue, 10 Jun 2025 12:28:26 GMT

Hi Menon ,

Ok, will get modem traces but it may be 1-2 weeks.

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

Menon — Tue, 10 Jun 2025 11:52:56 GMT

Hello,

Thank you for sharing the details. I will need to investigate this issue internally. Please collect the modem trace and share it with us, and also share any logs (if available) that might help narrow down the issue.

Kind regards,

Abhijith

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

teba99 — Fri, 06 Jun 2025 14:16:34 GMT

Hi Menon

Thanks for the reply. Build info below. Right now we only have UART debug logs with error messages as per above as well as SIM signaling logs from the carrier.

Modem traces are a good idea, we'll try to create those.

Thanks,
-- Terrence

nRF Connect SDK v2.9.0

Using Zephyr OS v3.7.99

Modem mfw_nrf91x1_2.0.2

CONFIG_NETWORKING=y

CONFIG_NET_SOCKETS=y

CONFIG_NET_SOCKETS_OFFLOAD=y

CONFIG_NET_MGMT_EVENT_STACK_SIZE=2048

CONFIG_NET_CONNECTION_MANAGER_MONITOR_STACK_SIZE=1024

CONFIG_NET_IPV4=y

CONFIG_NET_IPV6=y

CONFIG_NET_IPV6_NBR_CACHE=n

CONFIG_NET_IPV6_MLD=n

CONFIG_NET_CONNECTION_MANAGER=y

CONFIG_NRF_MODEM_LIB_NET_IF=y

CONFIG_NRF_MODEM_LIB_NET_IF_AUTO_DOWN=y

CONFIG_NRF_MODEM_LIB_NET_IF_DOWN_DEFAULT_LTE_DISCONNECT=y

CONFIG_LTE_PSM_REQ=n

CONFIG_NRF_MODEM_LIB=y

CONFIG_NRF_CLOUD_MQTT=y # This also enables FOTA by implicitly setting CONFIG_NRF_CLOUD_FOTA=y

CONFIG_NRF_CLOUD_MQTT_SHADOW_TRANSFORMS=y

CONFIG_MQTT_KEEPALIVE=120

CONFIG_LTE_LINK_CONTROL=y

CONFIG_SETTINGS=y

CONFIG_SETTINGS_FCB=y

CONFIG_FCB=y

RE: nRF9151 stuck in disconnected, unable to reconnect to LTE-M

Menon — Fri, 06 Jun 2025 14:00:43 GMT

Hello,

Could you share some more details, such as the nRF Connect SDK version and the modem firmware version? Are there any logs or error messages that could provide more information about the issue? Would you be able to collect the modem traces and share them here?

Kind regards,
Abhijith