[NRF9151] Modem does not connect after SIM deactivate/reactivate

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

dejans — Mon, 01 Sep 2025 10:32:05 GMT

Hi,

Achim Kraus Thank you for your input.
Mlgr I am sorry for delayed reply. I was out-of-office. Have you made any progress in the meantime? Can you provide status update?

Best regards,
Dejan

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Achim Kraus — Fri, 29 Aug 2025 14:24:33 GMT

[quote userid="5203" url="~/f/nordic-q-a/123007/nrf9151-modem-does-not-connect-after-sim-deactivate-reactivate/543421"]I did it with the snippets "west build -S nrf91-modem-trace-uart ..." and "west build -S nrf91-modem-trace-rtt ...".[/quote]

Oh, what a mess with the snippets and sysbuild!

-S will apply the snippet to all images, including the McuBoot one, therefore the errors.

(see MCUBOOT + NCS 3.0.1 + Snippets won't compile )

To fix that and apply the snippet only to the application, -D<app>_SNIPPET must be used, with the application folder name in <app>.

With that, also the modem trace with RTT works.

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Mlgr — Thu, 28 Aug 2025 09:30:52 GMT

Hello dejans ,

Do you have any news about our problem and the Jon's logs?

Best regards,

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Jon — Wed, 20 Aug 2025 08:42:00 GMT

Hello :)

Any idea on what we could do ?!

Best !

Jon

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Jon — Fri, 08 Aug 2025 16:27:26 GMT

So, I just couldn’t get modem traces working on the Thingy91X.
Every time I tried to use the required snippet, the build failed with:

I didn’t want to sink more time into debugging this for now — all I was doing was building the at_client example with the snippet.

Instead, I reproduced the exact same issue on an nRF9151 DK, this time with traces available.

Trace 1: before a power cycle
Trace 2: after the power cycle

The test scenario is the same as before:

Using a Tele2 SIM card (unsteered, all operators available)
SIM is activated at the beginning
Then deactivated
Perform a few modem power off/on cycles
Reactivate the SIM after a while

That’s when the board fails to reattach — even after a full power cycle.

devzone.nordicsemi.com/.../trace1.pcapng devzone.nordicsemi.com/.../trace2_5F00_posPowerCycle.pcapng

Best :)
Jon

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

dejans — Thu, 07 Aug 2025 06:32:41 GMT

Hi Mathieu,

Here is a list of links from documentation to help you in capturing modem traces:
cellular monitor
capturing modem trace using cellular monitor
capturing modem trace
nrf91 snippets
%XMODEMTRACE set
modem trace module

Best regards,
Dejan

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Achim Kraus — Wed, 06 Aug 2025 18:49:55 GMT

But you will still need to provide a modem trace for that case.

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Jon — Wed, 06 Aug 2025 18:13:46 GMT

This happens when i deactivate the sim manually, So this one is okay and happens as expected ;)🙂 but the problem occurs after that

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Achim Kraus — Wed, 06 Aug 2025 18:03:31 GMT

> EMM cause: 7

=> "EPS not allowed"

And that log is no modem trace ;-).

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Jon — Wed, 06 Aug 2025 15:12:11 GMT

i forgot to add, we tried this with 3 different Thingy91x, and with 2 different operators (TELE2 and Onomondo).
And of course, we have good network coverage in our office :)

Best

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Jon — Wed, 06 Aug 2025 15:06:03 GMT

Hi,

Here are some news :)
We were not able to plug our app with the tracing tools. But we are really stuck, so we changed our approch.

We reproduced the problem by using the Nordic modem shell example.

You will find attach all the command we did. At the beginning, we are able to reach the network, we generate the problem by deactivating the sim and reactivating it later after having done a at+CFUN=0 and at+CFUN1 (2/3 minutes after),

By the end of the file, you can see we tried several stuff to connect but it never work.

THe only way to reach the network again is by power cycling the thingy91x

What are your thoughts ?devzone.nordicsemi.com/.../serial_2D00_terminal_2D00_06082025_5F00_165918.txt

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

dejans — Tue, 29 Jul 2025 11:33:25 GMT

Hi,

For additional information about capturing modem traces, you can refer to these links in documentation
modem tracing and capturing modem trace using Cellular Monitor.

[quote user="JonJon"]Tomorrow, i will check with some TELE2 sim, and a brand new Thingy91X. I'll give you more infos then.[/quote]

I am looking forward to your update.

Best regards,
Dejan

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Jon — Mon, 28 Jul 2025 17:34:48 GMT

Hi !

We were not really able to make some progress.

We were not able to get modem traces. I was not able to do it with UART1, since the uart1 is used for other purposes, and the connectivy_bridge is not used anymore. That's why we redirect all our app uart to RTT.

So, i tried to use the RTT modem trace snippet.
I also get the -63 error.

By the way, i get nothing on channel 2, about modem traces. It remains empty

Here is the command i used to build

of course, i used the link given for the snippet.

Well, it seems i won't be able to get some modem traces :)

About the operator, i tried with a Onomondo sim until now. My device connects to Bouygues Telecom Network (by using onomondo or Tele2).

Tomorrow, i will check with some TELE2 sim, and a brand new Thingy91X. I'll give you more infos then.

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

dejans — Thu, 24 Jul 2025 08:17:01 GMT

Hi Mathieu,

Have you made some progress?

Have you been able to capture modem trace, possibly following Achim's suggestion using modem trace snippet?

Which mobile network operator does your device connect to?

Due to frequent rebooting via watchdog, it could be that reset loop restriction was triggered.

Best regards,
Dejan

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Achim Kraus — Thu, 24 Jul 2025 05:58:53 GMT

I don't know, how Mathieu enabled the modem trace, in my test I did it with the snippets "west build -S nrf91-modem-trace-uart ..." and "west build -S nrf91-modem-trace-rtt ...".

With the UART it works, with RTT I wasn't able to get the trace and got only warnings in the logging console instead.

NCS 2.9.2, nRF9151-DK, mfw 2.0.2.

Ubuntu, JLinkRTTLogger V8.18

nrfjprog --reset && JLinkRTTLogger -Device NRF9151_XXCA -If SWD -Speed 50000 modemtracesrtt.bin

(As already mentioned above.)

But the modem trace is rather a side issue.

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

dejans — Wed, 23 Jul 2025 15:47:09 GMT

Hi,

Can you show how you enable tracing over UART and RTT?
You can read more about modem tracing and modem trace module in the documentation.

Best regards,
Dejan

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Mlgr — Wed, 23 Jul 2025 09:23:32 GMT

[quote userid="5203" url="~/f/nordic-q-a/123007/nrf9151-modem-does-not-connect-after-sim-deactivate-reactivate/543281"]

You added the power_off/normal cycle and the modem trace via RTT.

I would start removing both and retest. If you use versioning, that may be easier to checkout a last working version and retest that.

And then adding one change step by step and see, if both stops the device from working or just one.

[/quote]

That’s the problem: I flashed the same software that worked two weeks ago, but now this board won’t connect, even though it connects fine on another board. I think we received a defective batch, I’ve already thrown away five or six boards.

The modem sends a “Searching” event and then does nothing. That’s why I tried enabling modem tracing. But when I read its output over UART the data appears garbled, even though my DTS settings (baud rate, pins, etc.) are correct and I’m using 1,000,000 baud / 8 data bits / 1 start bit / 1 stop bit / no parity. I don’t know why the output isn’t legible, so I’m switching to RTT instead.

I really don’t understand why I’m having modem issues; I’ve never seen this with the Thingy:91 and I haven’t changed anything in my code.

On startup I call:

nrf_modem_lib_init()
modem_info_init()
modem_info_rsrp_register()
lte_lc_connect_async()

On shutdown I call:

lte_lc_offline()

I have another board running exactly the same software and it works fine (I’d rather not deactivate/reactivate its SIM because I need it for something else).

Am I doing something wrong in my initialization sequence?

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Achim Kraus — Wed, 23 Jul 2025 06:39:18 GMT

[quote userid="139584" url="~/f/nordic-q-a/123007/nrf9151-modem-does-not-connect-after-sim-deactivate-reactivate/543240"]I haven’t changed anything in this software version, and it was working fine two weeks ago. I’m really lost.[/quote]

You added the power_off/normal cycle and the modem trace via RTT.

I would start removing both and retest. If you use versioning, that may be easier to checkout a last working version and retest that.

And then adding one change step by step and see, if both stops the device from working or just one.

----------------------------------------------------------------------------------------

I'm used to trace the mode via UART and sometimes use the FLASH to keep a the trace for a time span (and afterward write that to the UART).

I never tried the RTT interface for the modem trace before, but at least using a nRF9151-DK, NCS 2.9.2, Ubuntu doesn't work for me either. I enabled it via the snippet, it start to report quite a lot of "trace_backend.write failed with err: -63". But using

nrfjprog --reset && JLinkRTTLogger -Device NRF9151_XXCA -If SWD -Speed 50000 modemtracesrtt.bin

(see How to capture nrf9160 modem traces using RTT? )

only reports:

SEGGER J-Link RTT Logger
Compiled Mar 5 2025 14:51:21
(c) 2016-2017 SEGGER Microcontroller GmbH, www.segger.com
Solutions for real time microcontroller applications

Default logfile path: /home/achim/.config/SEGGER

------------------------------------------------------------

------------------------------------------------------------
Connected to:
SEGGER J-Link (unknown)
S/N: 1051240195

Searching for RTT Control Block...OK.
3 up-channels found:
0: Terminal
1:
2:
Selected RTT Channel description:
Index: 1
Name:
Size: 0 bytes.

Output file: modemtracesrtt.bin

Getting RTT data from target. Press any key to quit.
------------------------------------------------------------

Transfer rate: 0 Bytes/s Data written: 0 Bytes 0

Not sure, may be this requires someone from Nordic to retest the modem trace via RTT.

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Mlgr — Tue, 22 Jul 2025 16:49:33 GMT

I tried retesting using the lte_lc_power_off / lte_lc_normal cycle on disconnection, but now my device doesn’t connect at all, it just hangs after the “Searching” event (the same thing happens when I deactivate/reactivate the SIM but this SIM was always activated).

I enabled tracing as described here: https://docs.nordicsemi.com/bundle/ncs-2.9.0/page/nrf/libraries/modem/nrf_modem_lib/nrf_modem_lib_trace.html, but all I get are these logs:

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Achim Kraus — Mon, 21 Jul 2025 09:07:37 GMT

[quote userid="139584" url="~/f/nordic-q-a/123007/nrf9151-modem-does-not-connect-after-sim-deactivate-reactivate/542972"]If I understand correctly, the calls to lte_lc_power_off and lte_lc_normal should work.[/quote]

Yes, that was my experience with the nRF9160/mfw1.3.7 and is now the same in the retest with the nRF9151/mfw2.0.2.

[quote userid="139584" url="~/f/nordic-q-a/123007/nrf9151-modem-does-not-connect-after-sim-deactivate-reactivate/542972"]I’ll retry them and increase the watchdog timeout to give the modem enough time to reconnect without being reset during the process.[/quote]

It should be at least worth to be tested.

[quote userid="139584" url="~/f/nordic-q-a/123007/nrf9151-modem-does-not-connect-after-sim-deactivate-reactivate/542972"]I’ll let you know the results.[/quote]

I'm looking forward.

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Mlgr — Mon, 21 Jul 2025 09:04:28 GMT

If I understand correctly, the calls to lte_lc_power_off and lte_lc_normal should work.

I’ll retry them and increase the watchdog timeout to give the modem enough time to reconnect without being reset during the process.

I’ll let you know the results.

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Achim Kraus — Mon, 21 Jul 2025 08:59:33 GMT

If 5 minutes are OK depends on the bands, the modes and the available networks. If you want to ensure, that this isn't the cause, just use 15 minutes and see, if that changes.

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Achim Kraus — Mon, 21 Jul 2025 08:56:08 GMT

[quote userid="5203" url="~/f/nordic-q-a/123007/nrf9151-modem-does-not-connect-after-sim-deactivate-reactivate/542963"]I will check the SIM deactivation/activation using 1nce and a nRF9151-DK. Let's see, what I get. [/quote]

I've tested it twice using a 1nce SIM.

In the first test, I activated the SIM after a couple of seconds, but the modem didn't test all the available TAC in that time. So the modem was able to reconnect to (a new) network without power-off/normal.

In the second test, I've waited until all available TAC rejected the modem with 15, before a activated the SIM again. Here it required the power-off/normal cycle as I was used to in the past.

But no watchdog, reboot nor power switch off-on cycle was required to get the modem connected again.

nRF9151-DK, NCS 2.9.2, mfw 2.0.2, nRF9151 LACA A0A

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Mlgr — Mon, 21 Jul 2025 08:17:57 GMT

The watchdog reboots the card after 5 minutes.

On reboot, the app restarts by calling (after initializing other components) nrf_modem_lib_init, modem_info_rsrp_register, and lte_lc_connect_async.

RE: [NRF9151] Modem does not connect after SIM deactivate/reactivate

Achim Kraus — Mon, 21 Jul 2025 08:10:29 GMT

[quote userid="139584" url="~/f/nordic-q-a/123007/nrf9151-modem-does-not-connect-after-sim-deactivate-reactivate/542962"](the watchdog still rebooted the card after a few minutes)[/quote]

That depends on how many "a few" are in numbers ;-).

Depending on the used bands and modes (LTE-M/NB-IoT) such a network search may take some more time. I usually start with 3 min and double that search time for each search after a quiet phase.